Conceptual Model
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| Concept | Definition |
|---|---|
| 4DPoint | Point described by three-dimensional (3D) coordinates and a time. |
| WorldGeodeticSystem1984 | WGS84 is an Earth-centered, Earth-fixed terrestrial reference system and geodetic datum adopted as the common geodetic reference frame for civil aviation. |
| WorldAreaForecastCentre | A meteorological centre designated to prepare and issue significant weather forecasts and upper-air forecasts in digital form on a global basis direct to States by appropriate means as part of the aeronautical fixed service. |
| WorkArea | A part of an aerodrome in which maintenance or construction works are in progress. |
| WindShearWarning | A message giving concise information on the observed or expected existence of wind shear which could adversely affect aircraft on the approach path or take-off path or during circling approach between runway level and 500 m. (1 600 ft) above that level and aircraft on the runway during the landing roll or take-off run. |
| WindShear | Local variation of the wind vector or any of its components in a given direction. |
| WindLayer | Vertically bounded area wind phenomenon, characterized by several attributes of type WindDirection, WindSpeed, a position and a height. |
| Wind | Air motion relative to the Earth's surface. Unless otherwise specified, only the horizontal component is considered. |
| WhenAbleProceedDirectToPosition | Instruction to proceed, when able, directly to the specified position. |
| WheelsOn | Event in which an aircraft touches down. |
| WheelsOff | Event in which an aircraft takes-off. |
| Weber | The magnetic flux which, linking a circuit of one turn, produces in it an electromotive force of 1 volt as it is reduced to zero at a uniform rate in 1 second. |
| WeatherRadar | Radar used to observe weather elements and phenomena. |
| WeatherPhenomenon | A meteorological event. |
| WeatherObserver | The agent responsible for manual weather observations. |
| WeatherLayer | An array of clouds and/or obscurations whose bases are at approximately the same level. |
| WeatherInformationSource | An automated or non-automated weather information source. |
| Waypoint | A specified geographical location used to define an area navigation route or the flight path of an aircraft employing area navigation. |
| Watt | The power which gives rise to the production of energy at the rate of 1 joule per second. |
| WaterLaneEnd | The end of the water lane (typically located at the furthest end of a turning basin) suitable for landing or takeoff runs of aircraft. WaterLaneEnds define the water lane and describe the approach/departure procedure characteristics of a water lane. |
| WarningArea | A non-regulatory airspace of defined dimensions designated over international waters that contains activity which may be hazardous to aircraft not participating in the activity. The purpose of such warning areas is to warn non participating pilots of the potential danger. |
| WarningAndAlerts | Message giving concise information of meteorological conditions which could adversely affect aircraft, during any phase of flight. |
| WakeTurbulenceCategory | A grouping of aircraft according to the effect of the rotating air mass created behind the wing tips. |
| VOR | A short-range, very-high-frequency omnidirectional beacon which provides an indication in the aircraft of the bearing of the beacon, or left-right track indication. |
| Volume | The measure of the physical space of any 3-D geometric object. |
| Volt | The unit of electric potential difference and electromotive force which is the difference of electric potential between two points of a conductor carrying a constant current of 1 ampere, when the power dissipated between these points is equal to 1 watt. |
| VOLMETService | The automatic provision of VOLMET information to aircraft in flight. |
| VOLMET | Meteorological information for aircraft in flight. |
| Volcano | A geological formation in form of an Earth crust opening/rupture, which allows hot magma, volcanic ash and gases from below the surface, escape into the atmosphere. |
| VolcanicAshSIGMET | A SIGMET that reports the presence of volcanic ash conditions. |
| VolcanicAshCloud | Ash contaminated atmospheric volume. |
| VolcanicAshAdvisoryCentre | A meteorological centre designated by regional air navigation agreement to provide advisory information to meteorological watch offices, area control centres, flight information centres, world area forecast centres and international OPMET databanks regarding the lateral and vertical extent and forecast movement of volcanic ash in the atmosphere following volcanic eruptions. |
| VolcanicAshAdvisory | Advisory information regarding the lateral and vertical extent and forecast movement of volcanic ash in the atmosphere following volcanic eruptions. |
| VolcanicAsh | Extremely fine particles of pulverized rock, the composition of which, generally speaking, is comprised predominantly of silica (> 50 per cent), together with smaller amounts of the oxides of aluminium, iron, calcium and sodium. |
| VolcanicActivityReport | A report on the occurrence of pre-eruption volcanic activity, volcanic eruptions or ash cloud. |
| VolcanicActivity | Volcanic unrest or eruption. |
| VoiceAutomaticTerminalInformationService | The provision of ATIS by means of continuous and repetitive voice broadcasts. |
| VisualNavigationAid | Any visual system which provides information to be used by the pilot or aircraft navigation systems for position determination or flight path guidance. |
| VisualManoeuvringCirclingArea | The area in which obstacle clearance should be taken into consideration for aircraft carrying out a circling approach. |
| VisualGroundGuidanceSystem | Any visual guidance systems used at aerodromes to help aircraft and other vehicles circulating on the platform to navigate from one location to another. This covers the markings and well as the light systems on the runways, taxiways, aprons. |
| VisualGlideSlopeIndicator | A visual guidance system that provides 'below/above glidepath' information to an aircraft executing an approach to a specific runway direction. |
| VisualFlightRules | A set of rules governing the conduct of flight under visual meteorological conditions. |
| VisualApproachProcedure | A series of predetermined manoeuvres by visual reference, from the initial approach fix, or where applicable, from the beginning of a defined arrival route to a point from which a landing can be completed and thereafter, if a landing is not completed, a go-around procedure can be carried out. |
| VHFDigitalLink | A constituent mobile subnetwork of the aeronautical telecommunication network (ATN), operating in the aeronautical mobile VHF frequency band. In addition, the VDL may provide non-ATN functions such as, for instance, digitized voice. |
| VGSIProtectionArea | An area protecting VGSI signal coverage by forbidding objects in the area. |
| VFRFlight | A flight conducted in accordance with the visual flight rules. |
| VerticalStructure | All fixed and mobile objects, or parts thereof that extend above the surface of the Earth. |
| VerticalSeparationMinima | The minimum difference between levels in terms of flight levels or altitudes between aircraft using prescribed altimeter setting procedures. |
| VerticalPathAngle | Angle of the published final approach descent in baro-VNAV procedures. |
| VerticalConstraint | A restriction brought to the vertical component of the trajectory of an aircraft. |
| VDLStation | An aircraft-based or ground-based physical entity, capable of VDL Mode 2, 3 or 4. |
| UpperFlightInformationRegion | An upper airspace of defined dimensions within which flight information service and alerting service are provided. |
| UpperAirObservingSystem | The upper-air observing program of NOAA, composed a network of ground-based remote-sensing wind profilers, en-route commercial aircraft in-situ observations (MDCRS), upper-air observations taken manually by pilots and disseminated by PIREPs, and of a network of rawinsonde stations (section 0). |
| UnplannedHolding | A specific holding procedure requested at an en-route fix on airway or route radials, bearings, or courses. |
| UnmannedAerialVehicle | An unmanned aerial vehicle is a pilotless aircraft, in the sense of Article 8 of the Convention on International Civil Aviation, which is flown without a pilot-in-command on-board and is either remotely and fully controlled from another place (ground, another aircraft, space) or programmed and fully autonomous. |
| UncertaintyPhase | A situation wherein uncertainty exists as to the safety of an aircraft and its occupants. |
| TypeCertificate | A document issued by a Contracting State to define the design of an aircraft type and to certify that this design meets the appropriate airworthiness requirements of that State. |
| TurningBasin | A water area used for the maneuvering of aircraft where the use of water surface is restricted. Turning basins should be located adjacent to shoreline facilities and at each end of the water operating area. |
| TurnHeading | Instruction to turn left or right as specified on to the specified heading. |
| TurnDegrees | Instruction to turn a specified number of degrees left or right. |
| TurnaroundTime | The time spent on the ground during a flight duty period between two flight sectors. |
| Turbulence | Atmospheric flow regime characterized by chaotic and stochastic property changes. This includes low momentum diffusion, high momentum convection, and rapid variation of pressure and velocity in space and time. |
| TrueAirspeed | The speed of the aeroplane relative to undisturbed air. |
| Tropopause | The boundary between the troposphere and the stratosphere, where an abrupt change in lapse rate usually occurs. |
| TropicalCycloneSIGMET | A SIGMET that reports the presence of a tropical cyclone. |
| TropicalCycloneAdvisoryCentre | A meteorological centre designated by regional air navigation agreement to provide advisory information to meteorological watch offices, world area forecast centres and international OPMET databanks regarding the position, forecast direction and speed of movement, central pressure and maximum surface wind of tropical cyclones. |
| TropicalCycloneAdvisory | Advisory information regarding the position, forecast direction and speed of movement, central pressure and maximum surface wind of a tropical cyclone. |
| TropicalCyclone | Cyclone of tropical origin of small diameter (some hundreds of kilometres) with minimum surface pressure in some cases less than 900 hPa, very violent winds and torrential rain; sometimes accompanied by thunderstorms. It usually contains a central region, known as the eye" of the storm, with a diameter of the order of some tens of kilometres, and with light winds and more or less lightly clouded sky." |
| TributaryStation | An aeronautical fixed station that may receive or transmit messages and/or digital data but which does not relay except for the purpose of serving similar stations connected through it to a communication centre. |
| TREND | A concise statement of the expected significant changes in the meteorological conditions at that aerodrome to be appended to a local routine or local special report, or a METAR or SPECI. |
| TransitionLevel | The lowest flight level available for use above the transition altitude. |
| TransitionLayer | The airspace between the transition altitude and the transition level. |
| TransitionAltitudeOrLevelCrossing | The event of reaching the transition altitude (in climb) or level (in descent). |
| TransitionAltitude | The altitude at or below which the vertical position of an aircraft is controlled by reference to altitudes. |
| TransferringUnitOrController | Air traffic control unit in the process of transferring the responsibility for providing air traffic control service to an aircraft to the next air traffic control unit along the route of flight. |
| TransferOfControlPoint | A defined point located along the flight path of an aircraft, at which the responsibility for providing air traffic control service to the aircraft is transferred from one control unit or control position to the next. |
| TrajectorySynchronisation | ATM activities aiming to obtain flight information and provide constraints onto the flight trajectory to achieve flow objectives and to conduct strategic Conflict management. |
| TrajectorySegment | A line connecting consecutive trajectory points. |
| TrajectoryPrediction | The process that estimates a future trajectory of an aircraft through computation. |
| TrajectoryPointUsage | The usage of a point when describing the movement of a flight. |
| TrajectoryPoint | A four dimensional point used in defining the flight path of an aircraft. |
| TrajectoryChangePoint | A trajectory point at which a vertical or lateral change, or a change of speed, happens. |
| Track | The projection on the earth's surface of the path of an aircraft, the direction of which path at any point is usually expressed in degrees from North (true, magnetic or grid). |
| Traceability | Ability to trace the history, application or location of that which is under consideration (ISO 9000). |
| ToweringCumulus | A descriptive term, used mostly in weather observing, for cumulus congestus (Cu con). |
| TouchDownLiftOffSafeArea | An obstacle-free area situated in the vicinity of a touchdown and lift-off area, provided to protect helicopters during manoeuvring, take-off and / or landing operations. |
| TouchDownLiftOff | A load bearing area on which a helicopter may touch down or lift off. |
| Touchdown | The point where the nominal glide path intercepts the runway. |
| TotalEstimatedElapsedTime | For IFR flights, the estimated time required from take-off to arrive over that designated point, defined by reference to navigation aids, from which it is intended that an instrument approach procedure will be commenced, or, if no navigation aid is associated with the destination aerodrome, to arrive over the destination aerodrome. For VFR flights, the estimated time required from take-off to arrive over the destination aerodrome. |
| TornadicVortex | A violently rotating column of air, usually pendant to a cumulonimbus, with circulation reaching the ground. It nearly always starts as a funnel cloud and may be accompanied by a loud roaring noise. |
| TopOfDescent | The trajectory point at which the trajectory begins a descent from the cruise flight level. |
| TopOfClimb | The trajectory point at which the trajectory arrives at the cruise flight level. There will be one top-of-climb for each cruise flight level (step climbs). |
| Tonne | The mass equal to 1 000 kilograms. |
| Timesheet | The definition of a single time interval, that occurs repeatedly as part of a schedule. |
| TimeOver | The time at which a flight arrives over a significant point. |
| TimeConstraint | A restriction brought to the time component of the trajectory of an aircraft. |
| Time | A finite extent or stretch of continued existence, as the interval separating two successive events or actions, or the period during which an action, condition, or state continues; a finite portion of time (in its infinite sense). |
| ThroughFlight | A particular operation of aircraft, identified by the operator by the use throughout of the same symbol, from point of origin via any intermediate points to point of destination. |
| Threshold | The beginning of that portion of the runway usable for landing. |
| Tesla | The magnetic flux density given by a magnetic flux of 1 weber per square metre. |
| Terrain | The surface of the Earth containing naturally occurring features such as mountains, hills, ridges, valleys, bodies of water, permanent ice and snow, and excluding obstacles. |
| TerminalProcedure | A series of predetermined manoeuvres with specified protection from obstacles. |
| TerminalControlArea | A control area normally established at the confluence of ATS routes in the vicinity of one or more major aerodromes. |
| TerminalCapacity | The number of passengers and tonnes of cargo per hour which can be processed in a terminal building (sometimes referred to as passenger throughput or cargo throughput). |
| TerminalArrivalAltitude | The lowest altitude that will provide a minimum clearance of 300 m (1 000 ft) above all objects located in an arc of a circle defined by a 46 km (25 NM) radius centred on the initial approach fix (IAF), or where there is no IAF on the intermediate approach fix (IF), delimited by straight lines joining the extremity of the arc to the IF. The combined TAAs associated with an approach procedure shall account for an area of 360 degrees around the IF. |
| Terminal | An installation on an aerodrome with facilities for loading and unloading aircraft and processing traffic (passengers, baggage, cargo and mail). |
| TemporarySegregatedArea | A defined volume of airspace normally under the jurisdiction of one aviation authority and temporarily segregated, by common agreement, for the exclusive use by another aviation authority and through which other traffic will not be allowed to transit. |
| TemporaryReservedArea | A defined volume of airspace normally under the jurisdiction of one aviation authority and temporarily reserved, by common agreement, for the specific use by another aviation authority and through which other traffic may be allowed to transit, under ATC clearance. |
| TemperatureInversion | Vertical temperature distribution such that temperature increases with height. |
| Temperature | The state of a substance or body with regard to sensible warmth or coldness, referred to some standard of comparison; spec. that quality or condition of a body which in degree varies directly with the amount of heat contained in the body, and inversely with its heat-capacity; commonly manifested by its imparting heat to, or receiving it from, contiguous bodies, and usually measured by means of a thermometer or similar instrument. |
| TaxiwayStrip | An area including a taxiway intended to protect an aircraft operating on the taxiway and to reduce the risk of damage to an aircraft accidentally running off the taxiway. |
| TaxiwayShoulder | An area adjacent to the edge of a taxiway so prepared as to provide a transition between the taxiway and the adjacent surface. |
| TaxiwayIntersection | A junction of two or more taxiways. |
| TaxiwayHoldingPosition | A designated position at which taxiing aircraft and vehicles must stop and hold position, unless otherwise authorized by the aerodrome control tower. |
| TaxiwayGuidanceLine | Guidance line painted on a taxiway. |
| Taxiway | A defined path on a land aerodrome established for the taxiing of aircraft and intended to provide a link between one part of the aerodrome and another, including: a) Aircraft stand taxilane. A portion of an apron designated as a taxiway and intended to provide access to aircraft stands only. b) Apron taxiway. A portion of a taxiway system located on an apron and intended to provide a through taxi route across the apron. c) Rapid exit taxiway. A taxiway connected to a runway at an acute angle and designed to allow landing aeroplanes to turn off at higher speeds than are achieved on other exit taxiways thereby minimizing runway occupancy times. |
| TaxiPhase | The phase of flight in which movement of an aircraft on the surface of an aerodrome under its own power occurs, excluding take-off and landing. |
| TaxiPath | A series of surface elements (expressed using aeronautical information elements). |
| TaxiInClearance | Information relating to the taxi-in clearance of an aircraft. |
| TaxiChannel | A water channel used for the movement of aircraft between on shore facilities and the water lane. |
| TargetStartUpApprovalTime | The time provided by ATC taking into account TOBT, CTOT and/or the traffic situation that an aircraft can expect to receive start up / push back approval. |
| TargetOffBlockTime | The time that an aircraft operator / handling agent estimates that an aircraft will be ready, all doors closed, boarding bridge removed, push back vehicle present, ready to start up / push back immediately upon reception of clearance from the TWR. |
| TakeOffWeight | The weight of the aircraft at the beginning of the take-off phase. |
| TakeOffTime | Time at which an aircraft leave the ground and becomes airborne. |
| TakeOffRunAvailable | The length of runway declared available and suitable for the ground run of an aeroplane taking off. |
| TakeOffRun | The phase of flight from the application of take-off power, through the take-off roll and rotation up to 50 feet [15 metres] above runway end elevation. |
| TakeOffPhase | The phase of flight from the application of take-off power until reaching the first prescribed power reduction, or until reaching the vfr pattern or 1,500 feet (450 metres) above runway end elevation, whichever comes first or the termination (abort) of the take-off. |
| TakeOffDistanceAvailableForHelicopter | The length of the FATO plus the length of helicopter clearway (if provided) declared available and suitable for helicopters to complete the take-off. |
| TakeOffDistanceAvailable | The length of the take-off run available plus the length of the clearway, if provided. |
| TakeOffConfiguration | Aircraft configuration for a given flight. It is the configuration at take-off"." |
| TAF | Message to transmit aerodrome forecasts and amendments prepared by the meteorological office designated the meteorological authority concerned. |
| TacticalOperationalPlanning | ATM activities starting near to the actual departure time of the flight (usually 24 hours preceding the flight) during which the ATM system has access to more accurate planning information. |
| TACAN | A navigation system developed by military and naval forces providing, as far as the navigating pilot is concerned and for suitably equipped aircraft, the same indication as a VOR/DME system. |
| SurvivalEquipment | Aircraft equipment that can be used by the crew and passengers to assist survival in harsh environments in case of emergency. |
| SurvivalELT | An ELT which is removable from an aircraft, stowed so as to facilitate its ready use in an emergency, and manually activated by survivors. |
| SurveillanceRadarElement | A component of a Precision Approach Radar System which, when installed, provides the orientation information required to direct the aircraft to the correct position and altitude so that the final approach can be instituted. |
| SurveillanceRadar | Radar equipment used to determine the position of an aircraft in range and azimuth. |
| SurfaceWeatherObservation | Surface weather observations provide numerous weather elements, that are observed by a variety of sensors, both measurable (e.g., pressure and temperature) and derived elements (e.g., density altitude). |
| SurfaceReport | A report containing observations of meteorological conditions made from the surface of the earth or water bodies. |
| SurfaceLevelHeliport | A heliport located on the ground or on the water. |
| SurfaceForecastReport | A report containing forecasts about surface meteorological conditions. |
| SurfaceContamination | Presence or removal of hazardous conditions on aerodrome movement areas due to snow, ice, slush, water. |
| SupercooledLargeDroplet | Liquid droplets with diameters greater than 0.05 mm (50 microns) at temperatures less than 0�C, i.e., freezing rain or freezing drizzle. Due to their relatively large size and high mass, SLD are particularly hazardous to aircraft, since they can impact the aircraft surfaces outside the ice-protected regions. |
| Subnetwork | An actual implementation of a data network that employs a homogeneous protocol and addressing plan, and is under the control of a single authority. |
| Stratus | Generally grey cloud layer with a fairly uniform base, which may give drizzle, ice prisms or snow grains. When the Sun is visible through the cloud, its outline is clearly discernible; Stratus does not produce halo phenomena except, possibly, at very low temperatures; sometimes it appears in the form of ragged patches. |
| Stopway | A defined rectangular area on the ground at the end of take-off run available prepared as a suitable area in which an aircraft can be stopped in the case of an abandoned take-off. |
| StayPhase | A period of 'special activity' when the aircraft will 'stay' in the area defined for a given length of time. |
| StateOfTheOperator | The State in which the operator's principal place of business is located or, if there is no such place of business, the operator's permanent residence. |
| StateOfRegistry | The State on whose register the aircraft is entered. |
| StateOfOrigin | The State in the territory of which the consignment was first loaded on an aircraft. |
| StateOfOccurrence | The State in the territory of which an accident or incident occurs. |
| StateOfManufacture | The State having jurisdiction over the organization responsible for the final assembly of the aircraft. |
| StateOfDesign | The State having jurisdiction over the organization responsible for the type design. |
| StateFlight | Operation of an aircraft used in military, customs or police service. |
| State | An internationally recognized geographic entity that provides air traffic service. |
| StartUpClearance | Approval from air traffic control to proceed with the Start-Up. |
| StartUpApprovalTime | Time at which the Start-Up of the aircraft engines is approved. |
| StartUp | The start up of the aircraft engines by the flight crew upon the ATC approval. |
| StartOfTakeOffRoll | The start of takeoff roll. |
| StartOfExpectVectors | The start of the vectoring, when procedures specify Expect Vectors"." |
| StandingPhase | The phase of flight from the time the first person boards the aircraft with the intention of flight until push-back or, if pushback does not apply, until taxiing from the gate or parking position is commenced. Subsequently, from engine shut down upon reaching the gate or parking position after flight until the last person has exited the aircraft. |
| StandardLevelTable | A table of consecutive cruising levels described under vertical separation criteria limited by an upper and lower level and used by General Air Traffic. |
| StandardLevelSector | The general rule by which standard level columns are used in a national airspace or within a region. |
| StandardLevelColumn | A column of consecutive cruising levels within a standard level table. |
| StandardInstrumentDeparture | A designated instrument flight rule (IFR) departure route linking the aerodrome or a specified runway of the aerodrome with a specified significant point, normally on a designated ATS route, at which the en-route phase of a flight commences. |
| StandardInstrumentArrival | A designated instrument flight rule (IFR) arrival route linking a significant point, normally on an ATS route, with a point from which a published instrument approach procedure can be commenced. |
| SSRCode | The number assigned to a particular multiple pulse reply signal transmitted by a transponder in Mode A or Mode C. |
| Squall | Atmospheric phenomenon characterized by an abrupt and large increase of wind speed with a duration of the order of minutes which diminishes rather suddenly. It is often accompanied by showers or thunderstorms. |
| Spray | Ensemble of water droplets torn by the wind from the surface of an extensive body of water, generally from the wave crests, and carried up a short distance into the air. |
| SpeedSchedule | A climb and a descent speed schedule comprised of a target Indicated Airspeed and Mach representing speed targets for the flight in transition assuming no flight-specific constraints. |
| SpeedConstraint | A restriction brought to the speed component of the trajectory of an aircraft. |
| SpeedChange | A change in speed during the execution of the flight. |
| SpecialVFRFlight | A VFR flight cleared by air traffic control to operate within a control zone in meteorological conditions below VMC. |
| SpecialRequirementsFlight | A flight that is expected to be operating in accordance with regulations issued by the relevant State for aircraft operating as State aircraft, as per Article 3 of the Convention on International Civil Aviation (Doc 7300), and for aircraft operating in accordance with State regulations for non-standard flying activities, normally through the use of reserved airspace. |
| SpecialRadioNavaid | Wide area (worldwide) navigation systems based on a chain of land or maritime stations providing radio frequency signals which can be used by airborne equipment to determine at least, the mobile two-dimensional position. |
| SpecialHandling | Special consideration given to the flight by ATS units. |
| SpaceWeather | The physical and phenomenological state of the natural space environment, including the Sun and the interplanetary and planetary environments. |
| SolarRadiation | Electromagnetic radiation emitted by the Sun with a spectrum close to the one of a black body with a temperature of 5770 K. The radiation peaks in visible wavelengths. When compared to the terrestrial radiation it is often referred to as shortwave radiation. |
| SolarFlare | Bright eruption from the Sun's chromosphere. Solar flares are classified in terms of the area of chromosphere affected, the duration of the phenomenon, and the width of the Ha line of hydrogen, on a scale ranging from 1- (minor eruption) to 3+ (very large eruption). |
| SNOWTAMService | SNOWTAM service. |
| SNOWTAM | A special series NOTAM notifying the presence or removal of hazardous conditions due to snow, ice, slush or standing water associated with snow, slush and ice on the movement area, by means of a specific format. |
| SnowPellets | Precipitation of white and opaque ice particles, which fall from a cloud and which are generally conical or rounded, with diameters attaining as much as 5 mm. |
| SnowGrains | Precipitation of very small opaque white particles of ice which fall from a cloud and which are fairly flat or elongated with diameters generally less than 1 mm. |
| Snow | Precipitation of ice crystals, isolated or agglomerated, falling from a cloud. |
| Smoke | Suspension in the atmosphere of small particles produced by combustion. |
| SmallHail | Precipitation of translucent ice particles, which falls from a cloud. These particles are almost always spherical and sometimes have conical tips. Their diameter may attain or even exceed five millimetres. |
| SlotSwapping | A tactical ATFM measure aiming at swapping departure slots that can be applied either manually or via automated means. |
| SimplifiedDirectionalFacility | A radio navigation aid providing a final approach course similar to, but less precise than, that of the ILS localizer. |
| SignificantPoint | A specified geographical location used in defining an ATS route or the flight path of an aircraft and for other navigation and ATS purposes. |
| SIGMET | Information issued by a meteorological watch office concerning the occurrence or expected occurrence of specified en-route weather phenomena which may affect the safety of aircraft operations. |
| Sievert | The unit of radiation dose equivalent corresponding to 1 joule per kilogram. |
| Siemens | The electric conductance of a conductor in which a current of 1 ampere is produced by an electric potential difference of 1 volt. |
| Shoulder | An area adjacent to the edge of a pavement so prepared as to provide a transition between the pavement and the adjacent surface. |
| ShipboardHeliport | A heliport located on a ship that may be purpose or non-purpose-built. A purpose-built shipboard heliport is one designed specifically for helicopter operations. A non-purpose-built shipboard heliport is one that utilizes an area of the ship that is capable of supporting a helicopter but not designed specifically for that task. |
| ServiceProviderCallsign | Information about the operational identifier by which the provider of the service is called and the language used. |
| Separator | The agent responsible for separation provision for a conflict, being either the airspace user or a separation provision service provider. |
| SeparationProvision | The tactical process of keeping aircraft away from hazards by at least the appropriate separation minima. |
| SeparationMode | An approved set of rules, procedures and conditions of application associated with separation minima. |
| SeparationMinima | The minimum displacements between an aircraft and a hazard which maintain the risk of collision at an acceptable level of safety. |
| SendingUnitOrController | Air traffic services unit/air traffic controller transmitting a message. |
| SegmentPoint | A point associated with a defined segment. |
| SegmentLeg | A part of an instrument or visual flight procedure defined by two consecutive significant points. |
| SegmentedCircleAirportMarkerSystem | A minimum installation consisting of a segmented circle located off the traffic area with a conventional wind cone located at its center, which may be supplemented with other pilot aids and traffic control devices required to meet the conditions existing at a particular airport. |
| SecondarySurveillanceRadar | A surveillance radar system which uses transmitters/receivers (interrogators) and transponders. |
| SearchAndRescueService | The performance of distress monitoring, communication, coordination and search and rescue functions, initial medical assistance or medical evacuation, through the use of public and private resources, including cooperating aircraft, vessels and other craft and installations. |
| SearchAndRescueService | The performance of distress monitoring, communication, coordination and search and rescue functions, initial medical assistance or medical evacuation, through the use of public and private resources, including cooperating aircraft, vessels and other craft and installations. |
| SeaplaneRampSite | Ramps specifically designed to transit seaplanes from land to water and vice versa. |
| SeaplaneRampCentreline | The centerline of ramps specifically designed to transit seaplanes to or from land or water. |
| SeaplaneLandingArea | A defined area on water at an aerodrome prescribed for the landing and take-off of seaplanes. |
| SchedulingAndStrategicActivities | ATM activities whereby airspace users perform mission planning, aerodrome operators plan to ensure the demand does not exceed available surface resources and ATM service providers determine if reallocation of resources to better meet the demand and if changes to airspace organization are required to optimize the allocation of resources. |
| ScheduledInternationalAirService | A series of flights that possesses all of the following characteristics: - it passes through the airspace over the territory of more than one State; - it is performed by aircraft for the transport of passengers, mail or cargo for remuneration, in such a manner that each flight is open to use by members of the public; and - it is operated so as to serve traffic between the same two or more points, either according to a published timetable or with flights so regular or frequent that they constitute a recognizable systematic series. |
| ScheduledAirService | An air service open to use by the general public and operated according to a published timetable or with such a regular frequency that it constitutes an easily recognizable systematic series of flights. |
| SatelliteWeatherObservingSystem | Weather satellites transmit visible imagery for daytime observing, infrared photos for both day and night observing and water vapor imagery that identify locations of moist and dry air (important for thunderstorm forecasting). Satellite imagery and data are also detection sources of convection, volcanic ash, ceiling, and fog products used in flight planning. |
| SandStorm | An ensemble of particles of sand energetically lifted to great heights by a strong and turbulent wind. |
| Sand | A material consisting of comminuted fragments and water-worn particles of rocks (mainly silicious) finer than those of which gravel is composed. |
| SafetySensitivePersonnel | Persons who might endanger aviation safety if they perform their duties and functions improperly including, but not limited to, crew members, aircraft maintenance personnel and air traffic controllers. |
| SafetyArea | A defined area on a heliport surrounding the FATO which is free of obstacles, other than those required for air navigation purposes, and intended to reduce the risk of damage to helicopters accidentally diverging from the FATO. |
| RunwayVisualRangeSystem | A meteorological equipment providing information about the distance over which the pilot of an aircraft on the centre line of a runway can see the runway surface markings or the lights delineating the runway or identifying its centre line. |
| RunwayVisualRange | The range over which the pilot of an aircraft on the centre line of a runway can see the runway surface markings or the lights delineating the runway or identifying its centre line. |
| RunwayTurnPad | A defined area on a land aerodrome adjacent to a runway for the purpose of completing a 180-degree turn on a runway. |
| RunwayStrip | A defined area including the runway and stopway, if provided, intended: a) to reduce the risk of damage to aircraft running off a runway; and b) to protect aircraft flying over it during take-off or landing operations. |
| RunwayShoulder | An area adjacent to the edge of a runway so prepared as to provide a transition between the runway and the adjacent surface. |
| RunwaySafetyArea | A defined surface surrounding the runway prepared or suitable for reducing the risk of damage to airplanes in the event of an undershoot, overshoot, or excursion from the runway. |
| RunwayProtectionArea | An area situated in the vicinity of a runway or provided to protect aircraft during manoeuvring, take-off and landing operations. |
| RunwayHoldingPosition | A designated position intended to protect a runway, an obstacle limitation surface, or an ILS/MLS critical/sensitive area at which taxiing aircraft and vehicles shall stop and hold, unless otherwise authorized by the aerodrome control tower. |
| RunwayEndSafetyArea | An area symmetrical about the extended runway centre line and adjacent to the end of the strip primarily intended to reduce the risk of damage to an aeroplane undershooting or overrunning the runway. |
| RunwayDirection | One of the two possible landing and/or take-off directions of a runway or Final Approach and Take-off Area (FATO). |
| RunwayDeclaredDistance | A conventional operational distance declared for a runway direction. |
| RunwayCrossingClearance | The clearance required to cross or operate on any active/inactive or closed runway. |
| RunwayCentrelinePoint | An operationally significant position on the centre line of a runway direction. |
| RunwayCentreLine | A theoretical line parallel to the direction of the runway partitioning into two equal parts. This line is materialised by marking and a runway centreline light system which can be extended beyond the runway threshold in order to guide landing aircraft to the runway. |
| RunwayCapacity | The number of aircraft movements which aeronautical authorities determine can safely be operated, usually stated as the total number of landings and take-offs per hour, taking into account such factors as the physical characteristics of the runways and the surrounding area, altitude, the types of aircraft involved (larger aircraft may mandate greater separation) and air traffic control (approach and aerodrome control) capabilities. |
| RunwayBlastPad | Specially prepared surface placed adjacent to the end of a runway to eliminate the erosive effect of the high wind forces produced by airplanes at the beginning of their take-off rolls. |
| Runway | A defined rectangular area on a land aerodrome prepared for the landing and take-off of aircraft. |
| RulesProcedures | An instruction or regulation that needs to be considered by personnel involved in flight operations in relation with an aerodrome or an airspace. |
| RouteSegment | A route or portion of route usually flown without an intermediate stop. |
| RoutePortion | A group of two or more consecutive segments of the same route, which have the usage and/or the same flight restrictions. |
| RoutePoint | A specified geographical location used in defining a flight route. |
| RouteLayout | The way in which the parts of a route are arranged. |
| Role | The role of an agent in an Organization. This describes the abstract role, any specific instance is modeled using membership". Notice that the notion of "role" combines the concepts of an agent "holding" the role and an organization "defining" and legally "owning" it." |
| Road | An established surface route on the movement area meant for the exclusive use of vehicles. |
| ResumeNormalSpeed | Instruction that the aircraft's normal speed be resumed. The previously issued speed restriction(s) are cancelled. |
| RestrictedUseAreaVisualAid | Marking and/or lighting intended to indicate runways and taxiways, or areas in their vicinity where restrictions of use apply. |
| RestrictedArea | An airspace of defined dimensions, above the land areas or territorial waters of a State, within which the flight of aircraft is restricted in accordance with certain specified conditions. |
| Resolution | A number of units or digits to which a measured or calculated value is expressed and used. |
| RescueCoordinationCentre | A unit responsible for promoting efficient organization of search and rescue services and for coordinating the conduct of search and rescue operations within a search and rescue region. |
| RequiredNavigationPerformance | A statement of the navigation performance necessary for operation within a defined airspace. |
| RequiredCommunicationPerformance | A statement of the performance requirements for operational communication in support of specific ATM functions. |
| ReportingPoint | A specified (named) geographical location in relation to which the position of an aircraft can be reported. |
| RepetitiveFlightPlan | A flight plan related to a series of frequently recurring, regularly operated individual flights with identical basic features, submitted by an operator for retention and repetitive use by ATS units. |
| ReliefFlight | Flight operated for humanitarian purposes which carried relief personnel and relief supplies such as food, clothing, shelter, medical and other items during or after an emergency and/or disaster and/or is used to evacuate persons from a place where their life or health is threatened by such emergency and/or disaster to a safe haven in the same State or another State willing to receive such persons. |
| RejoinRouteByTime | Instruction that the cleared flight route is to be rejoined at or before the specified time. |
| RejoinRouteByPosition | Instruction that the cleared flight route is to be rejoined at or before the specified time. |
| RejectedTakeOffDistanceAvailableForHelicopter | The length of the FATO declared available and suitable for helicopters operated in performance class 1 to complete a rejected take-off. |
| RegulatedAgent | An agent, freight forwarder or any other entity who conducts business with an operator and provides security controls that are accepted or required by the appropriate authority in respect of cargo or mail. |
| RegularStation | A station selected from those forming an en-route air-ground radiotelephony network to communicate with or to intercept communications from aircraft in normal conditions. |
| RegionalSpecializedMeteorologicalCentre | A specialized meteorological centre for the provision of transport model products for radiological environmental emergency response, at the request of the delegated authority of the State in which the radioactive material was released into the atmosphere, or the International Atomic Energy Agency (IAEA). |
| RegionalAirService | An air service offered on routes serving smaller cities within a region or between regions of a State; or an air service offered on secondary routes serving smaller cities in a regional area involving the territories of more than one State. |
| RegionalAirNavigationAgreement | Agreement approved by the Council of ICAO normally on the advice of a regional air navigation meeting. |
| Reflector | A reflector used with a precision approach radar. |
| ReduceToMinimumApproachSpeed | Instruction to reduce present speed to the minimum safe approach speed. |
| ReduceSpeedToSpeedOrLess | Instruction that the present speed is to be reduced to the specified speed, or less, and maintained at or below the specified speed until further advised. |
| ReduceSpeedToSpeed | Instruction that the present speed is to be reduced to the specified speed and maintained until further advised. |
| ReducedCoordinationArea | Portion of airspace of defined dimensions within which general aviation traffic is permitted off-route" without requiring general aviation traffic controllers to initiate co-ordination with OAT controllers." |
| ReceivingUnitOrController | Air traffic services unit/air traffic controller to which a message is sent. |
| ReachLevelByPosition | Instruction that a change of level is to continue, but at a rate such that the specified level is reached at or before the specified position. |
| RatedAirTrafficController | An air traffic controller holding a licence and valid ratings appropriate to the privileges to be exercised. |
| RapidExitTaxiway | A taxiway connected to a runway at an acute angle and designed to allow landing aeroplanes to turn off at higher speeds than are achieved on other exit taxiways thereby minimizing runway occupancy times. |
| Ranked4DTrajectory | A 4D trajectory proposed by airspace user or ASP as a potential agreed 4D trajectory. |
| Ranked4DTrajectories | A series of desired 4D trajectories, with tolerances supplied if necessary by the airspace user to define when the next ranked trajectory should be used. |
| Rain | Precipitation of liquid water particles, either in the form of drops of more than 0.5 mm in diameter, or of smaller widely scattered drops. |
| RadiotelephonyNetwork | A group of radiotelephony aeronautical stations which operate on and guard frequencies from the same family and which support each other in a defined manner to ensure maximum dependability of air-ground communications and dissemination of air-ground traffic. |
| RadioNavigationService | A service providing guidance information or position data for the efficient and safe operation of aircraft supported by one or more radio navigation aids. |
| RadioNavigationAid | Any electronic system which provides information to be used by the pilot or aircraft navigation systems for position determination or flight path guidance. |
| RadioFrequencyArea | A limitation, such as coverage, usability, etc., of a radio navigation aid or service frequency. |
| RadioCommunicationFailureMessage | Message transmitted when an ATS Unit is aware that an aircraft in its area is experiencing radio communications failure. Message transmitted to all subsequent ATS Units that have already received basic flight plan data and to the aerodrome control tower at the destination aerodrome, if basic flight plan data has been previously sent. If the next ATS Unit would receive flight plan information by current flight plan, the current flight plan and this message can be send and forwarded downstream. |
| RadioCommunicationChannel | A radio frequency band of sufficient width and associated identification data used for one- or two-way communication from or to a transmitter on the ground or in the air. |
| RadioAltimeterOperatingArea | A flat area established in the pre-threshold area of a precision approach runway to accommodate aeroplanes making auto-coupled approaches and automatic landings. |
| RadioactiveCloud | A radioactive particulate contaminated atmospheric area. |
| PublicAuthority | The agency or officials of a Contracting State responsible for the application and enforcement of the particular laws and regulations of that State which relate to any aspect of these Standards and Recommended Practices. |
| ProtectedAirspace | Airspace protected from specific air traffic. |
| ProhibitedArea | An airspace of defined dimensions, above the land areas or territorial waters of a State, within which the flight of aircraft is prohibited. |
| ProceedDirectToPosition | Instruction to proceed directly from its present position to the specified position. |
| ProcedureTransition | A group of consecutive segments that are part of a branch on an approach procedure, SID or STAR. |
| PrimarySurveillanceRadar | A surveillance radar system which uses reflected radio signals. |
| PreTacticalOperationalPlanning | ATM activities aiming to accommodate demand, once initial schedules have been provided and permissions have been obtained. |
| PrescribedEETReportingPoint | A point that has been prescribed for required Estimated Elapsed Time reporting. |
| PreliminaryFlightPlan | A flight plan provided by the operator to obtain the FF-ICE Planning service. |
| PreFlightInformationBulletin | A presentation of current NOTAM information of operational significance, prepared prior to flight. |
| PredictedGroundSpeed | The computed ground speed at the trajectory point. |
| PredictedAirspeed | The predicted indicated airspeed or Mach at the trajectory point. |
| PrecisionApproachRadarSystem | A system comprising a precision approach radar and a surveillance radar element. |
| PrecisionApproachRadar | Primary radar equipment used to determine the position of an aircraft during final approach, in terms of lateral and vertical deviations relative to a nominal approach path, and in range relative to touchdown. |
| PrecisionApproachProcedure | Precision approach (PA) procedure. An instrument approach procedure using precision lateral and vertical guidance with minima as determined by the category of operation. |
| Precipitation | Hydrometeor consisting of a fall of an ensemble of particles. The forms of precipitation are: rain, drizzle, snow, snow grains, snow pellets, diamond dust, hail and ice pellets. |
| PositionMarking | Location on the movement area surface used for Air Traffic Control clearances. Position marking could be a painted marking or a sign. |
| Position | Set of coordinates (latitude and longitude) referenced to the mathematical reference ellipsoid which define the position of a point on the surface of the Earth. |
| Polygon | A surface or area described by a closed line. |
| PointInSpaceReferencePoint | Reference point for the point-in-space approach as identified by the latitude and longitude of the MAPt. |
| PointInSpaceApproach | The point-in-space approach is based on a basic GNSS non-precision approach procedure designed for helicopters only. It is aligned with a reference point located to permit subsequent flight manoeuvring or approach and landing using visual manoeuvring in adequate visual conditions to see and avoid obstacles. |
| Point | The smallest unit of geometry which has no spatial extent. Points are described by two-dimensional (2D) or three-dimensional (3D) coordinates. |
| PilotInCommandUnderSupervision | Co-pilot performing, under the supervision of the pilot-in-command, the duties and functions of a pilot-in-command, in accordance with a method of supervision acceptable to the Licensing Authority. |
| PilotInCommand | The pilot designated by the operator, or in the case of general aviation, the owner, as being in command and charged with the safe conduct of a flight. |
| PilotControlledLighting | An indication that radio control of lighting is available to provide airborne control of lights by keying the aircraft's microphone. |
| Pier | A platform extending from a shore over water and supported by piles or pillars, used to secure, protect, and provide access to ships, boats, and seaplanes. |
| Person | A human being regarded as an individual. |
| Period | One-dimensional primitive representing an extent in time, a period is bounded by two different temporal positions. |
| PerformanceProfile | A zero-wind, standard atmosphere profile reflective of the flight capabilities and desired parameters. |
| PassengerService | The availability of passenger amenities and facilities at or in the vicinity of an aerodrome. |
| PassengerLoadingBridge | A mechanically operated, adjustable ramp to provide direct passenger access between aircraft and buildings. |
| PassengerAirService | An air service performed primarily for the transport of passengers. |
| Passenger | A person in or on a conveyance other than its driver, pilot, or crew. |
| OverPoint | The event of flying over a significant point. |
| OrthometricHeight | Height of a point related to the geoid, generally presented as an MSL elevation. |
| Organisation | A collection of people organized together into a community or other social, commercial or political structure. The group has some common purpose or reason for existence which goes beyond the set of people belonging to it, and can act as an agent. |
| OperatorsMaintenanceControlManual | A document which describes the operator's procedures necessary to ensure that all scheduled and unscheduled maintenance is performed on the operator's aircraft on time and in a controlled and satisfactory manner. |
| OperatorPreferences | A particular wish related to the planned trajectory. |
| OperatorFlightPriority | Indication of the relative priority of a flight within a group of flights for assignment of delays. |
| OperatorConstraint | Operator procedures and other specific operator information that may impact manoeuvers and clearances which they are unable to accept from ATC. |
| OperatorConfiguration | Aircraft configuration established by an aircraft operator for its fleet. |
| Operator | A person, organization or enterprise engaged in or offering to engage in an aircraft operation. |
| OperationsSpecifications | The authorizations, conditions and limitations associated with the air operator certificate and subject to the conditions in the operations manual. |
| OperationsManual | A manual containing procedures, instructions and guidance for use by operational personnel in the execution of their duties. |
| OperationalFlightPlan | The operator's plan for the safe conduct of the flight based on considerations of aeroplane performance, other operating limitations and relevant expected conditions on the route to be followed and at the aerodromes concerned. |
| OperationalFlightInformationService | The automatic provision of integrated messages containing meteorological information, information concerning radio navigation services and aerodromes to aircraft in flight. |
| Ohm | The electric resistance between two points of a conductor when a constant difference of potential of 1 volt, applied between these two points, produces in this conductor a current of 1 ampere, this conductor not being the source of any electromotive force. |
| OFISMessage | A message integrating, for the purposes of broadcasting, meteorological information, information concerning radio navigation services and aerodromes. |
| OffsetOfRoute | Instruction to fly a parallel track to the cleared route at a displacement of the specified distance in the specified direction. |
| OffBlockTime | Time at which the aircraft departs from its parking position. |
| OffBlockReadyTime | Time at which the aircraft is ready for Off-Block. |
| OffBlockReady | Event at which all doors of an aircraft are closed and departure will be possible immediately after reception of the ATC clearance. |
| OffBlock | The departure of the aircraft from its parking position. |
| Obstruction | The highest airspace, obstacle or terrain relative to a prescribed plane within a specified area. |
| ObstacleVisualAid | Marking and/or lighting intended to reduce hazards to aircraft by indicating the presence of obstacles. |
| ObstacleFreeZone | The airspace above the inner approach surface, inner transitional surfaces, and balked landing surface and that portion of the strip bounded by these surfaces, which is not penetrated by any fixed obstacle other than a low-mass and frangibly mounted one required for air navigation purposes. |
| ObstacleClearanceHeight | The lowest height above the elevation of the relevant runway threshold or the aerodrome elevation as applicable, used in establishing compliance with appropriate obstacle clearance criteria. |
| ObstacleClearanceAltitude | The lowest altitude above the elevation of the relevant runway threshold or the aerodrome elevation as applicable, used in establishing compliance with appropriate obstacle clearance criteria. |
| ObstacleAssessmentArea | The geometry of surfaces used to define the altitude the length of a segment, holding pattern, etc., in function of the obstructions located in the area. |
| ObstacleArea | An area used for the purpose of collecting obstacle data, as necessary for air navigation systems or functions. |
| Obstacle | All fixed (whether temporary or permanent) and mobile objects, or parts thereof, that: a) are located on an area intended for the surface movement of aircraft; or b) extend above a defined surface intended to protect aircraft in flight; or c) stand outside those defined surfaces and that have been assessed as being a hazard to air navigation. |
| ObservationReport | Information concerning the evaluation of one or more meteorological elements. |
| Obscuration | A weather phenomenon which reduces the visibility due to hydrometeor or lithometeor in suspension in the air. |
| NoTransgressionZone | In the context of independent parallel approaches, a corridor of airspace of defined dimensions located centrally between the two extended runway centre lines, where a penetration by an aircraft requires a controller intervention to manoeuvre any threatened aircraft on the adjacent approach. |
| NOTAMService | Provision of NOTAM service, as defined by ICAO Annex 15. |
| NOTAMCode | A comprehensive description of information contained in NOTAM. |
| NOTAM | A notice distributed by means of telecommunication containing information concerning the establishment, condition or change in any aeronautical facility, service, procedure or hazard, the timely knowledge of which is essential to personnel concerned with flight operations. |
| NoSpeedRestriction | Notification that the aircraft may keep its preferred speed without restriction. |
| NormalOperatingZone | Airspace of defined dimensions extending to either side of an ILS localizer course and/or MLS final approach track. Only the inner half of the normal operating zone is taken into account in independent parallel approaches. |
| NormalDescent | FR: Descent from cruise to either Initial Approach Fix (IAF) or VFR pattern entry. VFR: Descent from cruise to the VFR pattern entry or 1000 feet above the runway elevation, whichever comes first. |
| NonScheduledRevenueOperation | Charter flight or special flight performed for remuneration other than scheduled flight. |
| NonScheduledOperation | Any air service that is performed other than as a scheduled air service, including but not limited to charter operations. |
| NonScheduledInternationalFlight | Any international flight performed other than as a scheduled international air service. |
| NonPrecisionApproachProcedure | Non-precision approach (NPA) procedure. An instrument approach procedure which utilizes lateral guidance but does not utilize vertical guidance. |
| NonMovementArea | Area where aircraft cannot be seen by a control tower and therefore are restricted to move. |
| NonAutomatedWeatherObservationSource | Weather sources that tend to be manual in nature. |
| NonAutomatedWeatherObservationInstrument | Non-Automated Weather Observation Instrument |
| Nimbostratus | Grey cloud layer, often dark, the appearance of which is rendered diffuse by more or less continuously falling rain or snow, which in most cases reaches the ground. It is thick enough throughout to blot out the Sun. Low, ragged clouds frequently occur below the layer, with which they may or may not merge. |
| Night | The hours between the end of evening civil twilight and the beginning of morning civil twilight or such other period between sunset and sunrise, as may be prescribed by the appropriate authority. |
| Newton | The force which when applied to a body having a mass of 1 kilogram gives it an acceleration of 1 metre per second squared. |
| NetworkStation | An aeronautical station forming part of a radiotelephony network. |
| Negotiating4DTrajectory | A 4D trajectory proposed by airspace user or ASP as a potential agreed 4D trajectory. |
| NDB | A low or medium radio navigation service transmitting signals whereby the pilot of a suitably equipped aircraft can determine bearings, 'home in' on, and/or track to or from the station. |
| NavigationAreaSector | Subdivision of a sector to allow for different altitudes or gradients. |
| NavigationArea | An area specified by sectors with altitude or procedure descent gradient limitations for omnidirectional departures or Pilot navigation area. |
| NavigationAidInfrastructure | Space-based and or ground-based navigation aids available to meet the requirements in the navigation specification. |
| NauticalMile | The length equal to 1 852 metres exactly. |
| NationalRegisteringAuthority | The authority maintaining the national register or, where appropriate, the part thereof, in which aircraft are registered. |
| NationalityMark | A nationality symbol included in the radio call signs allocated to the State of Registry by the International Telecommunication Union. |
| MovementPreference | Movement preferences submitted by flight planners for consideration by the TFM automation in the event that a Traffic Management Initiative becomes necessary. For example: preferring a southerly course deviation if a re-route is necessary, preferring a ground delay over a reroute for pre-departure flights, any reroute less than 120 nm or less is acceptable, etc. |
| MovementArea | That part of an aerodrome to be used for the take-off, landing and taxiing of aircraft, consisting of the manoeuvring area and the apron(s). |
| MountainWave | Atmospheric internal gravity waves, which are periodic changes of atmospheric pressure, temperature and orthometric height in a current of air. |
| MountainObscuration | Description of a visibility condition that is distinguished from IFR because ceilings, by definition, are described as above ground level" (AGL). In mountainous terrain clouds can form at altitudes significantly higher than the weather reporting station and at the same time nearby mountain tops may be obscured by low visibility. In these areas the ground level can also vary greatly over a small area. " |
| ModeSSubnetwork | A means of performing an interchange of digital data through the use of secondary surveillance radar (SSR) Mode S interrogators and transponders in accordance with defined protocols. |
| Mist | Suspension in the air of microscopic water droplets or wet hygroscopic particles which reduce the visibility at the Earth's surface. |
| Mission | Operation carried out by an aircraft or a group of aircraft used in military service. |
| MissedApproachProcedure | The procedure to be followed if the approach cannot be continued. |
| MissedApproachPoint | That point in an instrument approach procedure at or before which the prescribed missed approach procedure must be initiated in order to ensure that the minimum obstacle clearance is not infringed. |
| MissedApproachHoldingFix | A fix used in RNAV applications that marks the end of the missed approach segment and the centre point for the missed approach holding. |
| MinutesInTrail | A tactical ATFM measure expressed as the number of minutes required between successive aircraft. |
| MinimumSectorAltitude | The lowest altitude which may be used which will provide a minimum clearance of 300 m (1 000 ft) above all objects located in an area contained within a sector of a circle of 46 km (25 NM) radius centred on a radio aid to navigation. |
| MinimumObstacleClearanceAltitude | The minimum altitude for a defined segment of flight that provides the required obstacle clearance. |
| MinimumEnRouteAltitude | The altitude for an en-route segment that provides adequate reception of relevant navigation facilities and ATS communications, complies with the airspace structure and provides the required obstacle clearance. |
| MinimumDescentHeight | A specified height in a non-precision approach or circling approach below which descent must not be made without the required visual reference. |
| MinimumDescentAltitude | A specified altitude in a non-precision approach or circling approach below which descent must not be made without the required visual reference. |
| Minima | Vertical and horizontal visual minima for a procedure segment conditions such as aircraft category, navigation equipment usage, procedure type, altimeter, etc. |
| MilitaryTrainingRouteBuffer | A control area or portion thereof, established in the form of a corridor around a military training route in order to protect it from other traffic. |
| MilitaryFlight | Operations of the armed forces other than those for remuneration which should be covered under public transport operations. |
| MilesInTrail | A tactical ATFM measure expressed as the number of miles required between aircraft (in addition to the minimum longitudinal requirements) to meet a specific criterion which may be separation, airport, fix, altitude, sector or route specific. |
| MicrowaveLandingSystem | A precision approach and landing guidance system operating in the microwave spectrum, which provides position information and various ground-to-air data. |
| METREPORT | Local report on routine observations for dissemination at the aerodrome of origin. |
| Metre | The distance travelled by light in a vacuum during 1/299 792 458 of a second. |
| MeteorologicalWatchOffice | An office designated to provide information concerning the occurrence or expected occurrence of specified en-route weather and other phenomena in the atmosphere that may affect the safety of aircraft operations within its specified area of responsibility. |
| MeteorologicalReport | A statement of observed meteorological conditions related to a specified time and location. |
| MeteorologicalOffice | An office designated to provide meteorological service for international air navigation. |
| MeteorologicalObservation | The evaluation of one or more meteorological elements. |
| MeteorologicalForecast | A statement of expected meteorological conditions for a specified time or period, and for a specified area or portion of airspace. |
| MeteorologicalAuthority | The authority providing or arranging for the provision of meteorological service for international air navigation on behalf of a Contracting State. |
| METAR | Aerodrome report on routine observations for dissemination beyond the aerodrome of origin. |
| Membership | The nature of the membership of the agent. |
| MeanSeaLevel | The average location of the interface between the ocean and the atmosphere, over a period of time sufficiently long so that all random and periodic variations of short duration average to zero. |
| MaximumTakeOffWeight | The maximum weight at which the aircraft is certified for take-off due to structural or other limits. |
| MarkingBuoy | A floating object moored to the bottom in a particular place, as an aid to navigation or for other specific purposes. |
| Marking | A symbol or group of symbols displayed on the surface of the movement area in order to convey aeronautical information. |
| MarkerBeacon | A radio navigation service identifying a particular location in space by means of a 75 megahertz (MHz) transmitter which transmits a directional signal to be received by aircraft flying overhead. |
| MarineRailway | A seaplane hauling system using a rolling carriage running from the water to a repair facility ashore. The vessel to be hauled is floated to a position over the carriage and secured with chocks, then the carriage is hauled up the tracks using a cable winch. |
| ManufacturerConfiguration | Predefined aircraft configuration specified and delivered by the manufacturer of the aircraft or aircraft equipment(s). |
| ManualSurfaceWeatherObservation | Manual Surface Weather Observation |
| ManoeuvringArea | That part of an aerodrome to be used for the take-off, landing and taxiing of aircraft, excluding aprons. |
| MaintainSpeedOrLess | Instruction that the specified speed or a lesser speed is to be maintained. |
| MaintainSpeedOrGreater | Instruction that the specified speed or a greater speed is to be maintained. |
| MaintainSpeed | Instruction that the specified speed is to be maintained. |
| MaintainLevel | Instruction to maintain the specified level. |
| Lumen | The luminous flux emitted in a solid angle of 1 steradian by a point source having a uniform intensity of 1 candela. |
| LowLevelWindShear | Wind shear below 2000 feet AGL, exceeding 10 knots per 100 feet (vector difference between two points in space). |
| LongitudinalSeparationMinima | The minimum spacing between the estimated positions of the aircraft being separated. The spacing may be based on time or distance. |
| LogicalAcknowledgementMessage | A message transmitted by the computer of the accepting unit to indicate that a current flight plan or estimate message has been received and processed up to the point where the operational content will be received by the appropriate controller. This message shall only be used between ATC computers. |
| LocationIndicator | A four-letter code group formulated in accordance with rules prescribed by ICAO and assigned to the location of an aeronautical fixed station. |
| Location | An office or other premises at which the organization is located. |
| Litre | A unit of volume restricted to the measurement of liquids and gases which is equal to 1 cubic decimetre. |
| Line | A connected sequence of points. |
| Lightning | Luminous manifestation accompanying a sudden electrical discharge which takes place from or inside a cloud or, less often, from high structures on the ground or from mountains. |
| LicensingAuthority | The Authority designated by a Contracting State as responsible for the licensing of personnel. |
| LevelOffTouchdown | The phase of flight from the point of transition from nose-low to nose-up attitude, just before landing, until touchdown. |
| LevelChange | A change in level during the execution of the flight. |
| Level | A generic term relating to the vertical position of an aircraft in flight and meaning variously, height, altitude or flight level. |
| LateralSeparationMinima | The minimum distance (plus buffer) between intended routes of the aircraft being separated. |
| LateralConstraint | A restriction brought to the lateral component of the trajectory of an aircraft. |
| LateralChange | A change of course, track direction or heading during the execution of the flight. |
| LandingTime | Time at which an aircraft touches down. |
| LandingThresholdPoint | The LTP is a point over which the glide path passes at a relative height specified by the reference datum height. It is defined by the WGS-84 latitude, longitude and ellipsoid height. The LTP is normally located at the intersection of the runway centreline and threshold. |
| LandingRoll | The phase of flight from touchdown until the aircraft exits the landing runway or comes to a stop, whichever occurs first. |
| LandingPhase | The phase of flight from the point of transition from nose-low to nose-up attitude, immediately before landing (flare), through touchdown and until aircraft exits landing runway or comes to a stop, whichever occurs first. |
| LandingDistanceAvailableForHelicopter | The length of the FATO plus any additional area declared available and suitable for helicopters to complete the landing manoeuvre from a defined height. |
| LandingDistanceAvailable | The length of runway which is declared available and suitable for the ground run of an aeroplane landing. |
| LandingAndTakeOffFlightPhases | The LTO flight phases are composed by the Take-off, Landing, Climb Out, Approach, Taxi in, and Taxi Out. For Emissions impact assessments, the LTO phases are commonly associated to flight levels under FL30. |
| Knot | The speed equal to 1 nautical mile per hour. |
| Kilogram | The unit of mass equal to the mass of the international prototype of the kilogram. |
| Kelvin | A unit of thermodynamic temperature which is the fraction 1/273.16 of the thermodynamic temperature of the triple point of water. |
| Joule | The work done when the point of application of a force of 1 newton is displaced a distance of 1 metre in the direction of the force. |
| JetStream | Flat tubular, quasi-horizontal, current of air generally near the tropopause, whose axis is along a line of maximum speed and which is characterized by great speeds and strong vertical and horizontal wind shears. |
| IonosphericStorm | Turbulence in the F region of the ionosphere, usually due to a sudden burst of radiation from the Sun. |
| Intersection | A geographical location expressed as radials, bearings and/or distances from two radio navigation aids. |
| InternationalOperatingAgency | An agency of the kind contemplated in Article 77 of the Convention. |
| InternationalNOTAMOffice | An office designated by a State for the exchange of NOTAM internationally. |
| InternationalAirService | An air service that passes through the airspace over the territory of more than one State. |
| IntermediateFix | A fix that marks the end of an initial segment and the beginning of the intermediate segment. |
| IntermediateApproachSegment | That segment of an instrument approach procedure between either the intermediate approach fix and the final approach fix or point, or between the end of a reversal, racetrack or dead reckoning track procedure and the final approach fix or point, as appropriate. |
| Integrity | A degree of assurance that an aeronautical data and its value has not been lost nor altered since the data origination or authorized amendment. |
| IntegratedAeronauticalInformationPackage | A package which consists of the following elements: - AIP, including amendment service; - Supplements to the AIP; - NOTAM and PIB; - AIC; and - checklists and lists of valid NOTAM. |
| InstrumentLandingSystem | A combination of radio navigation services intended to facilitate aircraft in landing by providing lateral and vertical guidance including indications of distance from the optimum point of landing. |
| InstrumentFlightRules | A set of rules governing the conduct of flight under instrument meteorological conditions. |
| InstrumentApproachProcedure | A series of predetermined manoeuvres by reference to flight instruments with specified protection from obstacles from the initial approach fix, or where applicable, from the beginning of a defined arrival route to a point from which a landing can be completed and thereafter, if a landing is not completed, to a position at which holding or en-route obstacle clearance criteria apply. |
| Instant | The 0-dimensional primitive in time, equivalent to a point in space. An instant occupies a single temporal position in a given temporal reference system. |
| InitialPredictionPoint | The initial point at which a prediction was made. |
| InitialApproachSegment | That segment of an instrument approach procedure between the initial approach fix and the intermediate approach fix or, where applicable, the final approach fix or point. |
| InitialApproachFix | A fix that marks the beginning of the initial segment and the end of the arrival segment, if applicable. |
| InfrastructurePointUsage | The usage of a point when describing the Airspace or Base Infrastructure. |
| InfrastructurePoint | A point used in describing the base or airspace infrastructure. |
| InformationService | A service that consists in the provision of aeronautical, meteorological, traffic and related information to aircraft crew and other actors involved in flight operations, in flight or on the ground. |
| IndicatorAndSignalingDevice | Indicator enabling visual communication to a pilot, in particular in case of two ways communications failure, of some information important for landing (wind direction, runway in use direction). |
| IndicatedAirspeed | The uncorrected reading on the airspeed indicator. |
| IncreaseSpeedToSpeedOrGreater | Instruction that the present speed is to be increased to the specified speed or greater, and maintained at or above the specified speed until further advised. |
| IncreaseSpeedToSpeed | Instruction that the present speed is to be increased to the specified speed and maintained until further advised. |
| InCloudTurbulence | Upper-atmospheric turbulence encountered by an aircraft when flying through a cloud. |
| InBlockTime | The time that an aircraft arrives in-blocks. |
| InBlock | The arrival of the aircraft at its parking position. |
| Imbalance | An occurrence when the traffic demand exceeds the available capacity. |
| ILSProtectionArea | An area protecting ILS signal distortion by forbidding large objects in the area. |
| IFRFlight | A flight conducted in accordance with the instrument flight rules. |
| Icing | Formation of ice, rime, or hoarfrost on an aircraft in flight. |
| IcePellets | Precipitation of transparent particles of ice which are spherical or irregular, rarely conical, and which have a diameter of 5 mm or less. |
| IceCrystals | Any one of a number of macroscopic crystalline forms of ice including hexagonal columns and platelets, dendritic crystals, ice needles and their combinations. |
| ICAOAircraftTypeCode | The ICAO designator of an aircraft type as published in ICAO doc 8643. |
| ICAOAircraftCategory | Classification of aircraft according to specified basic characteristics, e.g. aeroplane, helicopter, glider, free balloon. |
| HoldingProcedure | A predetermined manoeuvre which keeps an aircraft within a specified airspace while awaiting further clearance. |
| HoldingFix | A geographical location that serves as a reference for a holding procedure. |
| HoldingBay | A defined area where aircraft can be held, or bypassed, to facilitate efficient surface movement of aircraft. |
| HoldingAssessment | The geometry of surfaces that define altitude levels and the structure of an area used to evaluate obstacles for determining holding patterns. |
| HoldExit | The event of exiting from planned holding. |
| HoldEntry | The event of entering into planned holding. |
| HoldAtPositionAsPublishedMaintainLevel | Instruction to enter a holding pattern with the published characteristics at the specified position and level. |
| Hoist | A hoist is a device used for lifting or lowering a load by means of a drum or lift-wheel around which rope or chain wraps. It may be manually operated, electrically or pneumatically driven and may use chain, fiber or wire rope as its lifting medium. The load is attached to the hoist by means of a lifting hook. |
| HighFrequencyDataLink | A constituent mobile subnetwork of the aeronautical telecommunication network (ATN), operating in the aeronautical mobile (R) high frequency bands. In addition, the HFDL may provide non-ATN functions, such as direct link service (DLS). The HFDL system must enable aircraft to exchange data with ground-based users. |
| Hertz | The frequency of a periodic phenomenon of which the period is 1 second. |
| Henry | The inductance of a closed circuit in which an electromotive force of 1 volt is produced when the electric current in the circuit varies uniformly at a rate of 1 ampere per second. |
| Heliport | An aerodrome or a defined area on a structure intended to be used wholly or in part for the arrival, departure and surface movement of helicopters. |
| Helideck | A heliport located on an offshore structure such as an exploration or production platform used for the exploitation of oil or gas. |
| HelicopterGroundTaxiwayAndTaxiRoute | A ground taxiway and taxi route intended for the ground movement of wheeled undercarriage helicopters. |
| HelicopterClearway | A defined area on the ground or water, selected and/or prepared as a suitable area over which a helicopter operated in performance class 1 may accelerate and achieve a specific height. |
| HelicopterAirTaxiwayAndTaxiRoute | A defined path on the surface established for the air taxiing of helicopters. |
| Height | The vertical distance of a level, a point or an object considered as a point, measured from a specified datum. |
| Heading | The direction in which the longitudinal axis of an aircraft is pointed, usually expressed in degrees from North (true, magnetic, compass or grid). |
| Haze | Suspension in the atmosphere of extremely small, dry particles which are invisible to the naked eye but numerous enough to give the sky an opalescent appearance. |
| Hazard | The objects or elements that an aircraft can be separated from. These are: other aircraft, terrain, weather, wake turbulence, incompatible airspace activity and, when the aircraft is on the ground, surface vehicles and other obstructions on the apron and manoeuvring area. |
| Hail | Precipitation of either transparent, or partly or completely opaque particles of ice (hailstones), usually spheroidal, conical or irregular in form and of diameter very generally between 5 and 50 millimetres, which falls from a cloud either separately or agglomerated into irregular lumps. |
| GuidanceLine | A line used to guide aircraft on and between airport movement areas. |
| GroundTrafficControlService | An ATC service provided for the purpose of: (a) preventing collisions on the manoeuvring area between aircraft and between aircraft and obstacles or vehicles; and (b) expediting and maintaining an orderly flow of aircraft operating on the manoeuvring area. |
| GroundStop | A tactical ATFM measure where some selected aircraft remain on the ground. |
| GroundLightSystem | One or more light sources located on the ground that provide visual assistance for air and ground navigation. |
| GroundHandling | Services necessary for an aircraft's arrival at, and departure from, an airport, other than air traffic services. |
| GroundEarthStation | An earth station in the fixed satellite service, or, in some cases, in the aeronautical mobile-satellite service, located at a specified fixed point on land to provide a feeder link for the aeronautical mobile satellite service. |
| GroundDelayProgramme | A strategic, pre-tactical, or tactical ATFM measure where aircraft are held on the ground in order to manage capacity and demand in a specific volume of airspace or at a specific airport. |
| GroundBasedFix | A specified geographical location used in describing the base or airspace infrastructure, which is found by reference to radio navigation aids. |
| GregorianCalendar | Calendar in general use; first introduced in 1582 to define a year that more closely approximates the tropical year than the Julian calendar (ISO 19108). |
| GlobalNavigationSatelliteSystem | A worldwide position and time determination system that includes one or more satellite constellations, aircraft receivers and system integrity monitoring, augmented as necessary to support the required navigation performance for the intended operation. |
| GloballyUniqueFlightIdentifier | A single reference for FF-ICE information pertinent to a flight that is unique globally. |
| GlidePath | A descent profile determined for vertical guidance during a final approach. |
| Geometry | Geometry constructs used to describe the physical shape of entities. |
| GeometricalTaxiRoute | Geometrical representation of TaxiRoute". The geometrical route consists of Nodes and Edges." |
| GeomagneticActivity | Disturbances in the geomagnetic field caused by gusts in the solar wind that blows by the Earth. |
| GeneralAviationOperation | An aircraft operation other than a commercial air transport operation or an aerial work operation. |
| GBASAzimuthReferencePoint | The GARP is defined to be beyond the FPAP along the procedure centreline by a fixed offset of 305 m (1 000 ft). It is used to establish the lateral deviation display limits. |
| Gate | Access to an airport terminal on the passenger side. |
| Gangway | A variable-sloped pedestrian walkway that links a fixed structure or land with a floating structure. |
| GAMET | An area forecast in abbreviated plain language for low-level flights for a flight information region or sub-area thereof, prepared by the meteorological office designated by the meteorological authority concerned and exchanged with meteorological offices in adjacent flight information regions, as agreed between the meteorological authorities concerned. |
| GalacticCosmicRay | Highly energetic radiation thought to be created by supernovae, etc., where the outer layers of an exploding star are shock-accelerated to enormous speeds. This radiation, primarily protons, crosses the galaxy and possibly even between galaxies. |
| G-SIGMET | A graphical SIGMET report. |
| G-AIRMET | A graphical AIRMET report. |
| FunnelCloud | Cloud formed at the core of a waterspout or tornado vortex, sometimes extending right down to the ground, caused by the reduction of pressure at the centre of the vortex. |
| FuelEndurance | The estimated maximum length of time the aircraft can spend in the cruise phase of flight, determined by the amount of fuel at take-off. |
| FreeTextEmergencyMessage | Generic message applicable in all situations when no standardised emergency of AIDC message can be applied. |
| FormationFlight | A flight consisting of more than one aircraft which, by prior arrangement between the pilots, operates as a single aircraft with regard to navigation and position reporting, as well as clearances issued by ATC. |
| FormalOrganisation | An organisation which is recognized in the world at large, in particular in legal jurisdiction, with associated rights and responsibilities |
| Forecast | A statement of expected meteorological conditions for a specified time or period, and for a specified area or portion of airspace. |
| Foot | The length equal to 0.304 8 metre exactly. |
| Fog | A suspension of very small, usually microscopic water droplets in the air, reducing visibility at the Earth's surface. |
| FlyoverWaypoint | A waypoint at which a turn is initiated in order to join the next segment of a route or procedure. |
| FlyHeading | Instruction to fly on the specified heading. |
| FlyByWaypoint | A waypoint which requires turn anticipation to allow tangential interception of the next segment of a route or procedure. |
| FloatingDockSite | Floating facility which can serve as a mooring place for vessels or as a floating dry dock. |
| FloatingBarge | A long, large, usually flatbottom boat for transporting freight that is generally unpowered and towed or pushed by other craft. A barge anchored offshore makes an excellent seaplane service facility. An office, lounge, or shop is normally included aboard and floating docks can be added alongside the barge. The barge may be anchored directly to the shore or to a pier by booms and a gangway or anchored offshore in a fixed position. |
| FlightStatus | An indication of whether a given aircraft requires special handling by air traffic services units or not. |
| FlightSafetyDocumentsSystem | A set of interrelated documentation established by the operator, compiling and organizing information necessary for flight and ground operations, and comprising, as a minimum, the operations manual and the operator's maintenance control manual. |
| FlightRulesChange | A change in flight rules during the execution of the flight. |
| FlightRules | The regulations that govern all aspects of operations under which the pilot flies. |
| FlightRoutingElement | An airspace, route or point that is concerned by a specified flight restriction. |
| FlightRoute | The path of a flight over the surface of the earth, including also altitude and speed information. |
| FlightRestrictionRoute | A sequence of routing elements (points, route portions or airspace) that must/must not appear in the specified order in the flight plan of an aircraft fulfilling the conditions of the related Flight Restriction. |
| FlightRestrictionLevel | A single level or a level band associated with a flight restriction, either condition or routing element. |
| FlightRestriction | A rule meant to regulate the use of the route network, by identifying a set of flights which fulfil a combination of elementary flow conditions and either forbidding them on a particular routing or obliging them to follow one routing out of a set of mandatory alternatives. |
| FlightPlan | Specified information provided to air traffic services units, relative to an intended flight or portion of a flight of an aircraft. |
| FlightPhase | A period-in-time occurrence during a Flight. |
| FlightPathAlignmentPoint | A point in the same lateral plane as the LTP or FTP that is used to define the alignment of the final approach segment. For approaches aligned with the runway centreline, the FPAP is located at or beyond the opposite threshold of the runway. The delta length offset from the opposite threshold of the runway defines its location. |
| FlightOperationsOfficerOrFlightDispatcher | A person designated by the operator to engage in the control and supervision of flight operations, whether licensed or not, suitably qualified in accordance with Annex 1, who supports, briefs and/or assists the pilot-in-command in the safe conduct of the flight. |
| FlightManual | A manual, associated with the certificate of airworthiness, containing limitations within which the aircraft is to be considered airworthy, and instructions and information necessary to the flight crew members for the safe operation of the aircraft. |
| FlightLevel | A surface of constant atmospheric pressure which is related to a specific pressure datum, 1 013.2 hectopascals (hPa), and is separated from other such surfaces by specific pressure intervals. |
| FlightIntent | The future aircraft trajectory expressed as a 4-D profile until destination (taking account of aircraft performance, weather, terrain, and ATM service constraints), calculated and owned" by the aircraft flight management system, and agreed by the pilot." |
| FlightInformationService | A service provided for the purpose of giving advice and information useful for the safe and efficient conduct of flights. |
| FlightInformationRegion | An airspace of defined dimensions within which flight information service and alerting service are provided. |
| FlightInformationCentre | A unit established to provide flight information service and alerting service. |
| FlightEvent | An event happening to a given flight. |
| FlightDeck | Term encompassing the flight crew and/or aircraft systems. |
| FlightCrewMember | A licensed crew member charged with duties essential to the operation of an aircraft during a flight duty period. |
| FlightCrewApplicationAndApproval | Equipment and procedures for which the air crew is qualified. |
| FlightConfiguration | Configuration of aircraft in operation. |
| FlightConditionElement | An operand in a flight condition combination. |
| FlightConditionCombination | A combination of conditions involving: 1) an operator such as \AND\", \"OR\", \"AND NOT\", \"SEQUENCE\", \"NONE\" and 2) one or more operands, each of these being either a condition element or another combination of conditions." |
| FlightCapability | The capabilities of the flight comprising of the: a) presence of relevant serviceable equipment on board the aircraft; b) equipment and capabilities commensurate with flight crew qualifications; and c) where applicable, authorization from the appropriate authority. |
| Flight | The operation of an aircraft which, in the case of a manned aircraft, takes place between the time any person boards the aircraft with the intention of flight until such time as all such persons have disembarked, or in the case of an unmanned aircraft, takes place between the time the aircraft is ready to move with the purpose of flight until such time as it comes to rest at the end of the flight and the primary propulsion system is shut down. |
| FixToleranceArea | An area surrounding an intersection within which the corresponding point may be. The dimensions of the fix tolerance area are determined by the system use accuracy of the navigation aid(s) on which the fix is based. |
| FixBalancing | A tactical ATFM measure aiming at distributing demand and avoiding delays whereby the aircraft is assigned a different arrival or departure fix than the one indicated in the flight plan. |
| FireFightingService | An airport service that provides rescue and fire fighting capabilities for aircraft in emergency at and around the airport. |
| FIRBoundaryCrossing | The event of crossing from one FIR into another. |
| FinalApproachTrack | The flight track in the final approach segment that is normally aligned with the runway centreline. For offset final approach segments, the final approach track is aligned with the orientation of the FTP and the FPAP. |
| FinalApproachSegment | That segment of an instrument approach procedure in which alignment and descent for landing are accomplished. |
| FinalApproachFix | That fix or point of an instrument approach procedure where the final approach segment commences. |
| FinalApproachAndTakeOffArea | A defined area over which the final phase of the approach manoeuvre to hover or landing is completed and from which the take-off manoeuvre is commenced. Where the FATO is to be used by helicopters operating in performance Class 1, the defined area includes the rejected take-off area available. |
| FinalApproach | That part of an instrument approach procedure which commences at the specified final approach fix or point, or where such a fix or point is not specified, a) at the end of the last procedure turn, base turn or inbound turn of a racetrack procedure, if specified; or b) at the point of interception of the last track specified in the approach procedure; and ends at a point in the vicinity of an aerodrome from which: 1) a landing can be made; or 2) a missed approach procedure is initiated. |
| FiledFlightPlan | The flight plan as filed with an ATS unit by the pilot or a designated representative, without any subsequent changes. |
| Filed4DTrajectory | The 4D trajectory filed by the FF-ICE enabled airspace user (eAU) with the FF-ICE enabled Air Traffic Management Service Providers (eASP). |
| FictitiousThresholdPoint | The FTP is a point over which the final approach segment path passes at a relative height specified by the reference datum height. It is defined by the WGS-84 latitude, longitude and ellipsoid height. The FTP replaces the LTP when the final approach course is not aligned with the runway extended centreline or when the threshold is displaced from the actual runway threshold. For non-aligned approaches the FTP lies on the intersection of the perpendicular from the FAS to the runway threshold. The FTP elevation is the same as the actual runway threshold elevation. |
| FFICEInformation | A generic construct representing the information that is exchanged globally between Airspace users, Aerodrome operators, ATM service providers, Airspace providers and Emergency service providers, as prescribed by ICAO Doc 9965. |
| Farad | The capacitance of a capacitor between the plates of which there appears a difference of potential of 1 volt when it is charged by a quantity of electricity equal to 1 coulomb. |
| ExtendedFlightOverWater | A flight operated over water at a distance of more than 93 km (50 NM), or 30 minutes at normal cruising speed, whichever is the lesser, away from land suitable for making an emergency landing. |
| ExitIntoConstrainedAirspace | The event of exiting from designated constrained airspace. |
| ExitFromRestrictedORReservedAirspace | The event of exiting from an airspace restriction/reservation. |
| Executed4DTrajectory | The actual 4D trajectory of the aircraft from the start-up to the present position. |
| Event | An action which occurs at an Instant. |
| EstimateMessage | A message transmitted by each ACC for flight information centre to the next ACC or flight information centre along the route of flight. It is transmitted at least 20 minutes before the time at which the aircraft is estimated to pass the transfer of control point or boundary point at which it comes under the control of such unit, unless another period of time has been prescribed by the appropriate ATS authority. |
| EstimatedTimeOver | The time at which it is estimated that the flight will pass a point on its intended trajectory. |
| EstimatedTimeOfArrival | For IFR flights, the time at which it is estimated that the aircraft will arrive over that designated point, defined by reference to navigation aids, from which it is intended that an instrument approach procedure will be commenced, or, if no navigation aid is associated with the aerodrome, the time at which the aircraft will arrive over the aerodrome. For VFR flights, the time at which it is estimated that the aircraft will arrive over the aerodrome. |
| EstimatedTakeOffWeight | The estimated takeoff weight of the aircraft. |
| EstimatedTakeOffTime | The estimated take-off time taking into account the Estimated Off-Block Time plus the Estimated Taxi-Out Time. |
| EstimatedOffBlockTime | The estimated time at which the aircraft will commence movement associated with departure. |
| EstimatedLandingTime | The estimated time that an aircraft will land. |
| EstimatedInBlockTime | The estimated time that an aircraft will arrive in-block. |
| EstimatedEndOfDeicingTime | The estimated time when de-icing operations on an aircraft are expected to end. |
| EstimatedElapsedTimeReporting | The reporting of the estimated elapsed time. |
| EstimatedElapsedTime | The estimated time required to proceed from one significant point to another. |
| EstimatedDeicingTime | Time difference between the Estimated End of De-icing Time (EEZT) minus the Estimated Commencement of De-icing Time (ECZT). |
| EstimatedCommencementOfDeicingTime | The estimated time when de-icing operations on an aircraft are expected to start. |
| EntryIntoConstrainedAirspace | The event of crossing into designated constrained airspace. |
| EntryIntoAnRestrictedOrReservedAirspace | The event of entering an airspace restriction/reservation. |
| EnRoutePhase | The phase of flight from the completion of initial climb at the departure aerodrome to the completion of controlled descent to the outer marker [ifr] or [vfr] to completion of the controlled descent to the vfr pattern or 1,500 feet [450 metres] above runway end elevation, whichever comes first. |
| EnRouteHolding | The phase of flight, in which a pre-determined ad-hoc manoeuvre occurs, which keeps the aircraft within a specified airspace en-route awaiting further instructions. |
| EnRouteDelay | A time duration for which a flight is expected to loiter; i.e. they will depart from IFR operations at the associated point and expect to request resumption of IFR operations after the indicated duration. |
| EnRouteClearance | A clearance covering the flight path of an aircraft after take-off to the point at which an approach to land is expected to commence. Note.- In some circumstances it may be necessary to subdivide this clearance, e.g. into sections divided by control area boundaries or into the departure, climb, or descent phases of flight. |
| Engine | A unit used or intended to be used for aircraft propulsion. It consists of at least those components and equipment necessary for functioning and control, but excludes the propeller/rotors (if applicable). |
| EndStay | The termination of an operation at which the flight remained for some time. |
| EndPredictionPoint | The final point at which a prediction was made. |
| EndOfLandingRoll | The event of coming to a full stop on the arrival runway. |
| EndOfExpectVectors | The end of the vectoring, when procedures specify Expect Vectors"." |
| EndDeicingTime | Time at which the deicing operation ends. |
| EmergencyPhase | A generic term meaning, as the case may be, uncertainty phase, alert phase or distress phase. |
| EmergencyMessage | Message used during emergency phases as per ICAO Annex 12, or other emergency (such as radio communications failure, unlawful interference or passenger illness). |
| EmergencyLocatorTransmitter | A generic term describing equipment which broadcast distinctive signals on designated frequencies and, depending on application, may be automatically activated by impact or be manually activated. |
| Embarkation | The boarding of an aircraft for the purpose of commencing a flight, except by such crew or passengers as have embarked on a previous stage of the same through-flight. |
| Elevation | The vertical distance of a point or a level, on or affixed to the surface of the earth, measured from mean sea level. |
| ElevatedHeliport | A heliport located on a raised structure on land. |
| DustWhirl | An ensemble of particles of dust or sand, sometimes accompanied by small litter, raised from the ground in the form of a whirling column of varying height with a small diameter and an approximately vertical axis. |
| DustStorm | An ensemble of particles of dust energetically lifted to great heights by a strong and turbulent wind. |
| Dust | Earth or other solid matter in a minute and fine state of subdivision, so that the particles are small and light enough to be easily raised and carried in a cloud by the wind; any substance comminuted or pulverized; powder. |
| Duration | Lasting, continuance in time; the continuance or length of time; the time during which a thing, action, or state continues. |
| Drizzle | Fairly uniform precipitation in very fine drops of water (diameter less than 0.5 mm) very close to one another, falling from a cloud. |
| DomesticAirService | An air service operated wholly within the territory of a State. |
| Document | A piece of written, printed, or electronic matter that provides information or evidence or that serves as an official record. |
| DockingArea | A defined area on a seaplane base either fixed or floating, intended to accommodate aircraft for purposes of loading or unloading passengers or cargo, refueling, parking, or maintenance. |
| DME | Ultra High Frequency (UHF) ground equipment that is used in conjunction with airborne equipment to determine distance between the airborne and ground equipment. |
| DistressPhase | A situation wherein there is reasonable certainty that an aircraft and its occupants are threatened by grave and imminent danger or require immediate assistance. |
| Disembarkation | The leaving of an aircraft after a landing, except by crew or passengers continuing on the next stage of the same through-flight. |
| DirectionFinder | An electronic device used to determine the position of a radio source by means of directional antennas, which receives the strongest radio signal when it is pointing directly at the transmitter. |
| DirectFlightSegment | A direct flight (DCT) between two specified significant points. |
| DiplomaticClearance | A special permission for military transport aircraft of the participants to fly over each other country's territory and to land at and take-off from military and civilian airports (to the exception of the airports and/or areas specifically mentioned in a list of exempted airports and/or areas to be completed by each participant) whilst adhering to all national rules, international agreements, ICAO rules, restrictions described in the national military and civilian Aeronautical Information Publications, ATC regulations, NOTAMs or other special requirements. |
| Desired4DTrajectory | The current 4D trajectory that is requested and generated by the airspace user with knowledge of the ATM system's operational constraints and resource contention. |
| DesignatedPoint | A geographical location not marked by the site of a radio navigation aid, used in defining an ATS route, the flight path of an aircraft or for other navigation or ATS purposes. |
| DescentFix | A fix established in a precision approach at the FAP to eliminate certain obstacles before the FAP, which would otherwise have to be considered for obstacle clearance purposes. |
| DescendToReachLevelByTime | Instruction that a descent is to commence at a rate such that the specified level is reached at or before the specified time. When this message element is not concatenated with another vertical clearance, the level specified is the assigned level which is to be maintained. |
| DescendToReachLevelByPosition | Instruction that a descent is to commence at a rate such that the specified level is reached at or before the specified position. When this message element is not concatenated with another vertical clearance, the level specified is the assigned level which is to be maintained. |
| DescendToLevel | Instruction that a descent to a specified level is to commence and once reached the specified level is to be maintained. |
| DescendAtVerticalRateMinimum | Instruction to descend at not less than the specified rate. |
| DescendAtVerticalRateMaximum | Instruction to descend at not above the specified rate. |
| DepartureSurfaceSegment | This segment describes the elements of the overall trajectory from the departure gate up to and including the departure runway. |
| DepartureOperations | The set of flight operations following procedures associated with the departure aerodrome. |
| DepartureMessage | A message transmitted (unless otherwise prescribed on the basis of regional air navigation agreements) immediately after the departure of an aircraft for which basic flight plan data (FPL) has been previously distributed. |
| DepartureClearance | Authorization for an aircraft to take-off under conditions specified by an air traffic control unit. |
| DepartureAirportSlotTime | The time of the Airport Departure Slot as allocated by the Airport Slot Coordinator |
| Demand | The number of aircraft requesting to use the ATM system in a given time period. |
| DelayMessage | A message transmitted when the departure of an aircraft, for which basic flight plan data (FPL) has been sent,is delayed by more than 30 minutes after the estimated off-block time contained in the basic flight plan data. |
| DeicingTime | Duration of the deicing operation. |
| DeicingGroup | A group of deicing areas. |
| DeicingArea | An area comprising an inner area for the parking of an aeroplane to receive de-icing / anti-icing treatment and an outer area for the manoeuvring of two or more mobile de-icing / anti-icing equipment. |
| Deicing | De-icing operation on an aircraft that may consist of removal of snow, ice or frost from the aircraft (de-icing), and/or also application of chemicals that remain on a surface and continue to delay the reformation of ice up (anti-icing). |
| DegreeCelsius | The special name for the unit kelvin for use in stating values of Celsius temperature. |
| DeclaredCapacity | A measure of the ability of the ATC system or any of its subsystems or operating positions to provide service to aircraft during normal activities. It is expressed as the number of aircraft entering a specified portion of the ATM infrastructure in a given period of time, taking due account of weather, ATC unit configuration, staff and equipment available, and any other factors that may affect the workload of the controller responsible for the infrastructure. |
| DecisionHeight | A specified height in the precision approach or approach with vertical guidance at which a missed approach must be initiated if the required visual reference to continue the approach has not been established. |
| DecisionAltitude | A specified altitude in the precision approach or approach with vertical guidance at which a missed approach must be initiated if the required visual reference to continue the approach has not been established. |
| DatumCrossingPoint | The DCP is a point on the glide path directly above the LTP or FTP at a height specified by the RDH. |
| DateTime | A DateTime is a combination of a date and a time type. |
| Date | A date gives values for year, month and day. |
| DataQuality | A degree or level of confidence that the data provided meet the requirements of the data user in terms of accuracy, resolution and integrity. |
| DataLinkVOLMETService | The provision of VOLMET via DataLink. |
| DataLinkAutomaticTerminalInformationService | The provision of ATIS via data link. |
| DangerArea | An airspace of defined dimensions within which activities dangerous to the flight of aircraft may exist at specified times. |
| CurrentFlightPlan | The flight plan, including changes, if any, brought about by subsequent clearances. This information is transmitted by each ATSU to the next ATSU in case no basic flight plan data (FPL) has already been distributed. |
| Cumulus | Detached cloud, generally dense and with sharp outlines, developing vertically in the form of rising mounds, domes or towers, of which the bulging upper part is often like a cauliflower. The sunlit parts are mostly brilliant white and the base is relatively dark and nearly horizontal. Sometimes Cumulus clouds are ragged. |
| Cumulonimbus | Dense and heavy cloud with a considerable mountain- or tower-shaped vertical extension. These clouds, the base of which is quite dark, may give rise to thunderstorms and generally heavy precipitation in the form of rain, snow, fine or large hail, sometimes accompanied by strong wind gusts. |
| CruisingSpeed | A true air speed maintained during a significant portion of a flight. |
| CruisingLevel | A level maintained during a significant portion of a flight. |
| CruiseReliefPilot | A flight crew member who is assigned to perform pilot tasks during cruise flight, to allow the pilot-in-command or a co-pilot to obtain planned rest. |
| CruisePhase | The phase of flight from the top of climb to cruise altitude, or flight level, to the start of the descent toward the destination aerodrome or landing site. |
| CruiseClimbSpeed | The true airspeed to be maintained during cruise climb. |
| CruiseClimb | An aeroplane cruising technique resulting in a net increase in altitude as the aeroplane mass decreases. |
| CrossPositionBetweenTimeAndTime | Instruction that the specified position is to be crossed at a time between the specified times. |
| CrossPositionBetweenLevelAndLevel | Instruction that the specified position is to be crossed at a level between the specified levels. |
| CrossPositionAtTime | Instruction that the specified position is to be crossed at the specified time. |
| CrossPositionAtSpeed | Instruction that the specified position is to be crossed at the specified speed and the specified speed is to be maintained until further advised. |
| CrossPositionAtOrBelowLevel | Instruction that the specified position is to be crossed at or below the specified level. |
| CrossPositionAtOrBeforeTime | Instruction that the specified position is to be crossed at or before the specified time. |
| CrossPositionAtOrAfterTime | Instruction that the specified position is to be crossed at or after the specified time. |
| CrossPositionAtOrAboveLevel | Instruction that the specified position is to be crossed at or above the specified level. |
| CrossPositionAtLevel | Instruction that the specified position is to be crossed at the specified level. This may require the aircraft to modify its climb or descent profile. |
| CrossPositionAtAndMaintainLevelAtSpeed | Instruction that the specified position is to be crossed at the specified level and speed, and the level and speed are to be maintained. |
| CrossPositionAtAndMaintainLevel | Instruction that the specified position is to be crossed at the specified level and that level is to be maintained when reached. |
| CrossOverAltitudePoint | The point in climb or descent where the airplane will transition between Mach and IAS control. |
| CrossBorderService | An international shorthaul air service operating across the borders of two contiguous States. |
| CrossBorderArea | Airspace of defined dimensions, above the land areas or territorial waters of more than one state. |
| CrewMember | A person assigned by an operator to duty on an aircraft during a flight duty period. |
| Course | The intended direction of travel of an aircraft, expressed in degrees from North (true, magnetic or grid). |
| Coulomb | The quantity of electricity transported in 1 second by a current of 1 ampere. |
| CorporateAviation | The non-commercial operation or use of aircraft by a company for the carriage of passengers or goods as an aid to the conduct of company business, flown by a professional pilot employed to fly the aircraft. (Note that corporate aviation is a subset of general aviation.) |
| Copilot | A licensed pilot serving in any piloting capacity other than as pilot-in-command but excluding a pilot who is on board the aircraft for the sole purpose of receiving flight instruction. |
| CoordinationMessage | A message transmitted in support of the coordination dialogue between ATS Units. |
| CoordinationAndTransfer | A dialogue procedure between ATC Units successively in control of a flight, comprising - notification of the flight - coordination of conditions of transfer by the transferring ATC unit - coordination, if necessary, and acceptance of conditions of transfer by the accepting ATC unit - transfer of control to the accepting ATC unit. |
| CoordinateReferenceSystem | Coordinate system that is related to the real world by a datum. |
| CoordinatedAirport | Any airport where, in order to land or take-off, it is necessary for an aircraft operator to have been allocated a slot by an appropriate authority. |
| ConvectionCell | A volume of convective air. |
| Convection | In the atmosphere, convection is the dominant vertical transport process in convective boundary layers, which are common over tropical oceans and, during sunny days, over continents. Moist convection in the atmosphere is characterized by deep, saturated updrafts and downdrafts, and unsaturated downdrafts driven by the evaporation and melting of precipitation. This form of convection is made visible by cumulus clouds and cumulonimbus clouds in the case of precipitation convection. |
| ControlZone | A controlled airspace extending upwards from the surface of the earth to a specified upper limit. |
| ControlSector | A subdivision of a designated control area within which responsibility is assigned to one controller or to a small group of controllers. |
| ControlledAirspace | An airspace of defined dimensions within which air traffic control service is provided in accordance with the airspace classification. |
| ControlAreaBoundaryPoint | A defined point on the control area boundary common to adjacent Air Traffic Service Units. |
| ControlArea | A controlled airspace extending upwards from a specified limit above the earth. |
| Contour | An estimated or observed outline of a particular weather situation. |
| ContinuePresentHeading | Instruction to continue to fly on the current heading. |
| ContactInformation | Information required to enable contact with the responsible person and/or organisation. |
| ConstrainedAirspaceCrossing | The event of crossing constrained airspace designated as a line. |
| ConflictHorizon | The extent to which hazards along the aircraft's future trajectory are considered for separation provision. |
| Conflict | Any situation involving an aircraft and a hazard in which the applicable separation minima may be compromised. |
| ConfigurationDeviationList | A list established by the organization responsible for the type design with the approval of the State of Design which identifies any external parts of an aircraft type which may be missing at the commencement of a flight, and which contains, where necessary, any information on associated operating limitations and performance correction. |
| CommonPoint | A point on the surface of the earth common to the tracks of two aircraft, used as a basis for the application of separation (e.g. significant point, waypoint, navigation aid, fix). |
| CommonMarkRegisteringAuthority | The authority maintaining the non-national register or, where appropriate, the part thereof, in which aircraft of an international operating agency are registered. |
| CommonMark | A mark assigned by the International Civil Aviation Organization to the common mark registering authority registering aircraft of an international operating agency on other than a national basis. |
| CommercialAirTransportOperation | An aircraft operation involving the transport of passengers, cargo or mail for remuneration or hire. |
| CommencementDeicingTime | Time at which the deicing operation commences. |
| Cloud | A hydrometeor consisting of minute particles of liquid water or ice, or of both, suspended in the free air and usually not touching the ground. It may also include larger particles of liquid water or ice and non-aqueous liquid or solid particles such as those present in fumes, smoke and dust. |
| ClockTime | A time is given by an hour, minute and second. |
| ClimbToReachLevelByTime | Instruction that a climb is to commence at a rate such that the specified level is reached at or before the specified time. When this message element is not concatenated with another vertical clearance, the level specified is the assigned level which is to be maintained. |
| ClimbToReachLevelByPosition | Instruction that a climb is to commence at a rate such that the specified level is reached at or before the specified position. When this message element is not concatenated with another vertical clearance, the level specified is the assigned level which is to be maintained. |
| ClimbToLevel | Instruction that a climb to a specified level is to commence and once reached the specified level is to be maintained. |
| ClimbToCruisingLevelOrAltitude | The phase of flight in which the climb from the completion of the initial climb to cruising level or altitude occurs. |
| ClimbAtVerticalRateMinimum | Instruction to climb at not less than the specified rate. |
| ClimbAtVerticalRateMaximum | Instruction to climb at not above the specified rate. |
| Clearway | A defined rectangular area on the ground or water under the control of the appropriate authority, selected or prepared as a suitable area over which an aeroplane may make a portion of its initial climb to a specified height. |
| ClearedRoute | Instruction to proceed via the specified route. |
| ClearAirTurbulence | Upper-atmospheric turbulence encountered by an aircraft when flying through clear air. |
| City | A town or other inhabited place. |
| Cirrus | Detached clouds in the form of white, delicate filaments or white or mostly white patches or narrow bands. These clouds have a fibrous (hair-like) appearance, or a silky sheen, or both. |
| Cirrostratus | Transparent, whitish cloud veil of fibrous (hair-like) or smooth appearance, totally or partially covering the sky, and generally producing halo phenomena. |
| Cirrocumulus | Thin, white patch, sheet or layer of cloud without shading, composed of very small elements in the form of grains, ripples, etc., merged or separated, and more or less regularly arranged; most of the elements have an apparent width of less than one degree. |
| CirclingApproach | An extension of an instrument approach procedure which provides for visual circling of the aerodrome prior to landing. |
| ChangeOverPoint | The point at which an aircraft navigating on an ATS route segment defined by reference to very high frequency omnidirectional radio ranges is expected to transfer its primary navigational reference from the facility behind the aircraft to the next facility ahead of the aircraft. |
| ChangeOfCruiseLevelPhase | The phase of flight during which the aircraft climbs, or descends, from one cruising flight level or altitude to the next cruising flight level or altitude. |
| ChangeMessage | A message transmitted when any change is to be made to the basic flight plan data (FPL). It is sent to all recipients of basic flight plan data affected by the change. |
| Ceiling | Height above the Earth's surface of the base of the lower cloud layer whose amount exceeds a specific value. |
| CDNMessage | A message transmitted during the coordination dialogue by an accepting unit to the transferring unit when the former wishes to propose a change to coordination data as contained in a previous current flight plan or estimate message. If the transferring unit wishes to propose a change to the data contained in a Coordination message, a coordination message shall be transmitted to the accepting unit. |
| CargoAirService | An air service provided for the public transport of freight and mail. |
| Cargo | Any property carried on an aircraft other than mail, stores and accompanied or mishandled baggage. |
| Capacity | The maximum number of aircraft that can be accommodated in a given time period by the system or one of its components (throughput). |
| Candela | The luminous intensity, in the perpendicular direction, of a surface of 1/600 000 square metre of black body at the temperature of freezing platinum under a pressure of 101 325 newtons per square metre. |
| CancellationMessage | A message transmitted when a flight, for which basic flight plan data (FPL) has been previously distributed, has been cancelled. |
| CalibratedAirspeed | Indicated airspeed corrected for instrument errors and position error (due to incorrect pressure at the static port caused by airflow disruption). |
| Calendar | Discrete temporal reference system that provides the basis for defining temporal position to a resolution of one day (ISO 19108). |
| CabinCrewMember | A crew member who performs, in the interest of safety of passengers, duties assigned by the operator or the pilot-in-command of the aircraft, but who shall not act as a flight crew member. |
| BusinessService | The provision of tangible goods, information, instructions or guidance. |
| BriefingService | Pre-flight and post-flight briefing service. |
| BridgeSide | Line representing the side extent of aerodrome feature(s) associated with the vertical drop section of an overpass. |
| Bridge | A structure forming or carrying a road over a river, a ravine, etc., or affording passage between two points at a height above the ground. |
| BeginStay | The beginning of an operation at which the flight will remain for some time. |
| Becquerel | The activity of a radionuclide having one spontaneous nuclear transition per second. |
| AuxiliaryPowerUnit | A self-contained power-unit on an aircraft providing electrical/pneumatic power to aircraft systems during ground operations. |
| AutomaticTerminalInformationService | The automatic provision of current, routine information to arriving and departing aircraft throughout 24 hours or a specified portion thereof. |
| AutomaticPortableELT | An automatically activated ELT which is rigidly attached to an aircraft but readily removable from the aircraft. |
| AutomaticFixedELT | An automatically activated ELT which is permanently attached to an aircraft. |
| AutomaticDeployableELT | An ELT which is rigidly attached to an aircraft and which is automatically deployed and activated by impact, and, in some cases, also by hydrostatic sensors. Manual deployment is also provided. |
| AutomaticDependentSurveillanceContract | A means by which the terms of an ADS-C agreement will be exchanged between the ground system and the aircraft, via a data link, specifying under what conditions ADS-C reports would be initiated, and what data would be contained in the reports. |
| AutomaticDependentSurveillanceBroadcast | A means by which aircraft, aerodrome vehicles and other objects can automatically transmit and/or receive data such as identification, position and additional data, as appropriate, in a broadcast mode via a data link. |
| AutomaticDependentSurveillance | A function for use by air traffic services (ATS) in which aircraft automatically transmit, via a data link, data derived from on-board navigation systems. As a minimum, the data include aircraft identification and three-dimensional position. Additional data may be provided as appropriate. |
| AutomatedWeatherObservationSystem | Automated sensor suites which are designed to serve aviation and meteorological observing needs for safe and efficient aviation operations and weather forecasting. |
| AuthorizedAgent | A person who represents an aircraft operator and who is authorized by or on behalf of such operator to act on formalities connected with the entry and clearance of the operator's aircraft, crew, passengers, cargo, mail, baggage or stores and includes, where national law permits, a third party authorized to handle cargo on the aircraft. |
| AuroralActivity | Natural light display in the sky particularly in the high latitude regions, caused by the collision of energetic charged particles with atoms in the high altitude atmosphere (thermosphere). |
| AtTimeProceedDirectToPosition | Instruction to proceed, at the specified time, directly to the specified position. |
| AtTimeDescendToLevel | Instruction that at a specified time a descent to a specified level is to commence and once reached the specified level is to be maintained. |
| AtTimeCrossPositionAtAndMaintainLevelAtSpeed | Instruction that at the specified time the specified position is to be crossed at the specified level and speed, and the level and speed are to be maintained. |
| AtTimeCrossPositionAtAndMaintainLevel | Instruction that at the specified time the specified position is to be crossed at the specified level and the level is to be maintained. |
| AtTimeClimbToLevel | Instruction that at the specified time a climb to the specified level is to commence and once reached the specified level is to be maintained. |
| ATSUnitLocationIndicator | A four-letter code group formulated in accordance with rules prescribed by ICAO and assigned to the ATS unit. |
| ATSSurveillanceSystem | A generic term meaning variously, ADS-B, PSR, SSR or any comparable ground-based system that enables the identification of aircraft. |
| ATSSurveillanceService | A term used to indicate a service provided directly by means of an ATS surveillance system. |
| ATSRoute | A specified route designed for channelling the flow of traffic as necessary for the provision of air traffic services. |
| AtPositionProceedDirectToPosition | Instruction to proceed, at the specified position, directly to the next specified position. |
| AtPositionDescendToLevel | Instruction that at the specified position a descent to the specified level is to commence and once reached the specified level is to be maintained. |
| AtPositionClimbToLevel | Instruction that at the specified time or position (exclusive) a climb to the specified level is to commence and once reached the specified level is to be maintained. |
| AtPositionClearedRoute | Instruction to proceed from the specified position via the specified route. |
| AtPositionClearedProcedure | Instruction to proceed from the specified position via the specified procedure. |
| AtNode | The event of arriving at an aerodrome surface routing network node. |
| ATMTrajectoryConstraint | Trajectory constraint imposed by the ATM system. |
| ATMPlanning | The ATFM phase during which the following measures are taken: a) reviewing airspace design (route structure and ATS sectors) and airspace utilization policies to look for potential capacity improvements; b) reviewing the technical infrastructure to assess the possibility of improving capacity. This is typically accomplished by upgrading various ATM support tools or enabling navigation, communications or surveillance infrastructure; c) reviewing and updating ATM procedures induced by changes to airspace design and technical infrastructure; d) reviewing staffing practices to evaluate the potential for matching staffing resources with workload and the eventual need for adjustments in staffing levels; and e) reviewing the training that has been developed and delivered to ATFM stakeholders. |
| ATMCommunity | The aggregate of organizations, agencies or entities that may participate, collaborate and cooperate in the planning, development, use, regulation, operation and maintenance of the ATM system. |
| AtLevelProceedDirectToPosition | Instruction to proceed, upon reaching the specified level, directly to the specified position. |
| ATISMessage | May contain: - meteorological information to be extracted from the local routine report (MET Report) or the local special report (SPECIAL) - aeronautical info from the NOTAM |
| ATFMPhase | A phase in which ATFM is carried out. |
| ATCInstruction | Directives issued by air traffic control for the purpose of requiring a pilot to take a specific action. |
| ATCClearance | Authorization for an aircraft to proceed under conditions specified by an air traffic control unit. |
| ATCBlindSpot | A location on an aerodrome movement area that is not visible to ATC personnel due to obstructions and is not designated as a Hot Spot. |
| AssumedAltimeterSetting | The altimeter setting that was used during prediction at this trajectory point for the computation of barometric altitude is provided. |
| ASHTAM | A special series NOTAM notifying by means of a specific format change in activity of a volcano, a volcanic eruption and/or volcanic ash cloud that is of significance to aircraft operations. |
| ArrivalSurfaceSegment | This segment describes the elements of the trajectory from the arrival runway, if applicable, to the arrival gate/stand. This segment reuses the same information items as for the departure surface segment, but in reverse. |
| ArrivalOperations | The set of flight operations following procedures associated with the destination aerodrome. |
| ArrivalMessage | A message transmitted by the appropriate ATS unit on receiving an arrival report. |
| ArrestingGear | A series of devices (for example: engaging or catching devices and energy absorption devices) that are used to stop an aircraft by absorbing its momentum in a routine landing, emergency landing or aborted take-off. |
| AreaReport | A meteorological report that includes information related to a region rather than a single point. |
| AreaOfCommonInterest | A route or portion of a route that is in close proximity to flight information boundaries. The extent is usually determined by the required separation minima. |
| AreaNavigationRoute | An ATS route established for the use of aircraft capable of employing area navigation. |
| AreaControlService | Air traffic control service for controlled flights in control areas. |
| AreaControlCentre | A unit established to provide air traffic control service to controlled flights in control areas under its jurisdiction. |
| ApronManagementService | A service provided to regulate the activities and the movement of aircraft and vehicles on an apron. |
| Apron | A defined area, on a land aerodrome/heliport, intended to accommodate aircraft/helicopters for purposes of loading and unloading passengers, mail or cargo, and for fuelling, parking or maintenance. |
| AppropriateAuthority | a) Regarding flight over the high seas: The relevant authority of the State of Registry. b) Regarding flight other than over the high seas: The relevant authority of the State having sovereignty over the territory being overflown. |
| AppropriateATSAuthority | The relevant authority designated by the State responsible for providing air traffic services in the airspace concerned. |
| ApproachSequence | The order in which two or more aircraft are cleared to approach to land at the aerodrome. |
| ApproachProcedureWithVerticalGuidance | An instrument approach procedure which utilizes lateral and vertical guidance but does not meet the requirements established for precision approach and landing operations. |
| ApproachPhase | The phase of flight from the outer marker to the to the point of transition from nose-low to nose-high attitude immediately prior to the flare above the runway [ifr]; or [vfr] from 1500 feet (450 metres) above the runway end elevation or from the point of vfr pattern entry to the flare above the runway. |
| ApproachLightingSystem | An airport lighting facility which provides visual guidance to landing aircraft by radiating light beams in a directional pattern by which the pilot aligns the aircraft with the final approach path for landing. |
| ApproachHolding | The phase of flight in which a pre-determined ad-hoc manoeuvre during the approach keeps the aircraft within a specified airspace awaiting further instructions. |
| ApproachControlUnit | A unit established to provide air traffic control service to controlled flights arriving at, or departing from, one or more aerodromes. |
| ApproachControlService | Air traffic control service for arriving or departing controlled flights. |
| AnchorageArea | An area designated specifically for the parking of seaplanes. |
| Ampere | The ampere is that constant electric current which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross-section, and placed 1 metre apart in a vacuum, would produce between these conductors a force equal to 2 x 10-7 newton per metre of length. |
| Altostratus | Greyish or bluish cloud sheet or layer of striated, fibrous or uniform appearance, totally or partly covering the sky, and having parts thin enough to reveal the Sun at least vaguely, as through ground glass. Altostratus does not show halo phenomena. |
| Altocumulus | White or grey, or both white and grey, patch, sheet or layer of cloud, generally with shading, composed of laminae, rounded masses, rolls, etc., which are sometimes partly fibrous or diffuse and which may or may not be merged; most of the regularly arranged small elements usually have an apparent width of between one and five degrees. |
| Altitude | The vertical distance of a level, a point or an object considered as a point, measured from mean sea level (MSL). |
| AltimeterSource | An instrument which measures vertical distance with respect to a reference level. |
| AltimeterSettingRegion | An airspace of defined dimensions within which standardized altimeter setting procedures apply. |
| AlongRouteDistance | The distance along the route. For an ASP-provided expanded route, it is computed from the first converted fix in the ASP's airspace for each route point in the expanded route. For an operator-provided expanded route, it is computed from the beginning of the route. |
| AlertPhase | A situation wherein apprehension exists as to the safety of an aircraft and its occupants. |
| AlertMessage | Message transmitted when an ATS Unit considers that an aircraft is in a state of emergency. Message is transmitted to all ATS Units that may be concerned with the flight and to the associated coordination centres. |
| AlertingService | A service provided to notify appropriate organizations regarding aircraft in need of search and rescue aid, and assist such organizations as required. |
| AlertArea | An airspace which may contain a high volume of pilot training activities or unusual type of aerial activity, neither of which is hazardous to aircraft. |
| Airway | A control area or portion thereof established in the form of a corridor. |
| AirTrafficServicesUnit | A generic term meaning variously, air traffic control unit, flight information centre or air traffic services reporting office. |
| AirTrafficServicesReportingOffice | A unit established for the purpose of receiving reports concerning air traffic services and flight plans submitted before departure. |
| AirTrafficServicesAirspaces | Airspaces of defined dimensions, alphabetically designated, within which specific types of flights may operate and for which air traffic services and rules of operation are specified. |
| AirTrafficService | A generic term meaning variously, flight information service, alerting service, air traffic advisory service, air traffic control service (area control service, approach control service or aerodrome control service). |
| AirTrafficManagementSystem | A system that provides ATM through the collaborative integration of humans, information, technology, facilities and services, supported by air and ground- and/or space-based communications, navigation and surveillance. |
| AirTrafficFlowManagement | A service established with the objective of contributing to a safe, orderly and expeditious flow of air traffic by ensuring that ATC capacity is utilized to the maximum extent possible and that the traffic volume is compatible with the capacities declared by the appropriate ATS authority. |
| AirTrafficControlUnit | A generic term meaning variously, area control centre, approach control unit or aerodrome control tower. |
| AirTrafficControlService | A service provided for the purpose of: a) preventing collisions: 1. between aircraft, and 2. on the manoeuvring area between aircraft and obstructions; and b) expediting and maintaining an orderly flow of air traffic. |
| AirTrafficAdvisoryService | A service provided within advisory airspace to ensure separation, in so far as practical, between aircraft which are operating on IFR flight plans. |
| AirTraffic | All aircraft in flight or operating on the manoeuvring area of an aerodrome. |
| AirTaxiService | A type of on-demand air service usually performed by small capacity aircraft on short notice in a very similar way to an automobile taxi service; or in some cases, a service operated on a scheduled basis with stops made only at points where passengers and cargo are to be picked up or discharged. |
| AirspaceUser | A generic term designating an organization operating aircraft and its pilots, the flight operations centres (FOC) responsible for the strategic planning of a flight and the entity responsible for the execution of a flight which is traditionally a flight deck. |
| AirspaceStatus | The activation status of the airspace. |
| AirspaceRestriction | A defined volume of airspace within which, variously, activities dangerous to the flight of aircraft may be conducted at specified times (a 'danger area'); or such airspace situated above the land areas or territorial waters of a State, within which the flight of aircraft is restricted in accordance with certain specified conditions (a 'restricted area'); or airspace situated above the land areas or territorial waters of a State, within which the flight of aircraft is prohibited (a 'prohibited area'). |
| AirspaceLocationIndicator | A four-letter code group formulated in accordance with rules prescribed by ICAO and assigned to the airspace. |
| AirspaceExit | The event of exiting an airspace. |
| AirspaceEntry | The event of entering an airspace. |
| AirspaceClassification | A classification of airspace which determines the operating rules, flight requirements, and services provided. |
| AirspaceClassG | Airspace Classification whereby IFR and VFR flights are permitted and receive flight information service if requested. |
| AirspaceClassF | Airspace Classification whereby IFR and VFR flights are permitted, all participating IFR flights receive an air traffic advisory service and all flights receive flight information service if requested. |
| AirspaceClassE | Airspace Classification whereby IFR and VFR flights are permitted, IFR flights are provided with air traffic control service and are separated from other IFR flights. All flights receive traffic information as far as is practical. Class E shall not be used for control zones. |
| AirspaceClassD | Airspace Classification whereby IFR and VFR flights are permitted and all flights are provided with air traffic control service, IFR flights are separated from other IFR flights and receive traffic information in respect of VFR flights, VFR flights receive traffic information in respect of all other flights. |
| AirspaceClassC | Airspace Classification whereby IFR and VFR flights are permitted, all flights are provided with air traffic control service and IFR flights are separated from other IFR flights and from VFR flights. VFR flights are separated from IFR flights and receive traffic information in respect of other VFR flights. |
| AirspaceClassB | Airspace Classification whereby IFR and VFR flights are permitted, all flights are provided with air traffic control service and are separated from each other. |
| AirspaceClassA | Airspace Classification whereby IFR flights only are permitted, all flights are provided with air traffic control service and are separated from each other. |
| Airspace | A defined three dimensional region of space relevant to air traffic. |
| AirService | iI its broadest sense, includes any service performed by aircraft for public transportation, whether on a scheduled or non-scheduled basis. For regulatory purposes, however, the term always has a specific meaning (defined in Article 96(a) of the Convention on International Civil Aviation and used in most bilateral air transport agreements between States) and refers to any scheduled air service performed by aircraft for the public transport of passengers, mail or cargo. |
| AirportSurveillanceRadar | A category of surveillance radars. ASR is designed to provide relatively short-range coverage in the general vicinity of an airport and to serve as an expeditious means of handling terminal area traffic through observation of precise aircraft locations on a radarscope. The ASR can also be used as an instrument approach aid. |
| AirportSuppliesService | A service that provides supplies (fuel, oil, oxygen, etc.) to aircraft. |
| AirportSlot | The scheduled time of arrival or departure available for allocation by, or as allocated by, a coordinator for an aircraft movement on a specific date at a coordinated airport. For scheduling purposes, the slot is the scheduled time of arrival or departure at the terminal, not the time of landing or take-off from the runway. An allocated slot will take account of all the coordination parameters at the airport e.g. runway(s), taxiways, aircraft parking stands, gates, terminal capacity (e.g. check-in and baggage delivery), environmental constraints e.g. night restrictions etc. |
| AirportGroundService | Services that provide maintenance of the airport infrastructure and direct support to aircraft on the ground. |
| AirportDepartureSlot | Permission given by a coordinator to use the full range of airport infrastructure necessary to operate an air service at a coordinated airport on a specific date and time for the purpose of take-off. |
| AirportClearanceService | An airport ground service providing clearance capabilities for airport surfaces. |
| AirportArrivalSlotTime | The time for the Airport Arrival Slot as allocated by the Airport Slot Coordinator |
| AirportArrivalSlot | Permission given by a coordinator to use the full range of airport infrastructure necessary to operate an air service at a coordinated airport on a specific date and time for the purpose of landing. |
| AirOperatorCertificate | A certificate authorizing an operator to carry out specified commercial air transport operations. |
| AIRMET | Information issued by a meteorological watch office concerning the occurrence or expected occurrence of specified en-route weather phenomena which may affect the safety of low-level aircraft operations and which was not already included in the forecast issued for low-level flights in the flight information region concerned or sub-area thereof. |
| Airline | As provided in Article 96 of the Convention, any air transport enterprise offering or operating a scheduled international air service. |
| AirFiledFlightPlan | A flight plan provided to an air traffic services unit by an aircraft during its flight. |
| AIREP | A report from an aircraft in flight prepared in conformity with requirements for position, and operational and/or meteorological reporting. |
| AirDefenceIdentificationZone | Special designated airspace of defined dimensions within which aircraft are required to comply with special identification and/or reporting procedures additional to those related to the provision of air traffic services (ATS). |
| AircraftWeight | A characteristic weight value of an aircraft. |
| AircraftTypeDesignator | A group of alphanumeric characters used to identify, in an abbreviated form, a type of aircraft. |
| AircraftType | The type of an aircraft. |
| AircraftState | A vector describing the current state of an aircraft or a vehicle, e.g. position, speed, acceleration. |
| AircraftStand | A designated area on an apron intended to be used for parking an aircraft. |
| AircraftSeries | A modifier, such as a numeral or sequential letter, denoting particular variations of a given aircraft model. |
| AircraftRegistration | A unique, alphanumeric string that identifies a civil aircraft and consists of the Aircraft Nationality or Common Mark and an additional alphanumeric string assigned by the state of registry or common mark registering authority. |
| AircraftOperatingManual | A manual, acceptable to the State of the Operator, containing normal, abnormal and emergency procedures, checklists, limitations, performance information, details of the aircraft systems and other material relevant to the operation of the aircraft. |
| AircraftObservation | The evaluation of one or more meteorological elements made from an aircraft in flight. |
| AircraftMovement | An aircraft take-off or landing at an airport. For aircraft traffic purposes one arrival and one departure is counted as two aircraft movements. |
| AircraftModel | Each of a set of aircraft designs for a given aircraft make. |
| AircraftMake | The aircraft brand. |
| AircraftIntent | Information on planned future aircraft behaviour, which can be obtained from the aircraft systems (avionics). It is associated with the commanded trajectory and will enhance airborne functions. The aircraft intent data correspond either to aircraft trajectory data that directly relate to the future aircraft trajectory as programmed inside the avionics, or the aircraft control parameters as managed by the automatic flight control system. These aircraft control parameters could either be entered by the flight crew or automatically derived by the flight management system. |
| AircraftIdentification | A group of letters, figures or a combination thereof which is either identical to, or the coded equivalent of, the aircraft call sign to be used in air-ground communications, and which is used to identify the aircraft in ground-ground air traffic services communications. |
| AircraftGroundService | The availability of maintenance, support and/or supply operations to aircraft at an aerodrome. |
| AircraftEquipment | Articles, including first-aid and survival equipment and commissary supplies, but not spare parts or stores, for use on board an aircraft during flight. |
| AircraftEarthStation | A mobile earth station in the aeronautical mobile-satellite service located on board an aircraft. |
| AircraftConfiguration | An arrangement of one or more aircraft equipments in a particular form, figure, or combination. |
| AircraftCategory | The aircraft categorization according to a set of criteria. |
| AircraftCapability | The ability of an aircraft or an aircraft equipment to provide a service or perform a function that, either on its own or with other services or functions, can deliver a definable level of performance. This level of performance is measurable within a framework of performance indicators and safety requirements. |
| AircraftAvionics | Any electronic device - including its electrical part - for use in an aircraft, including radio, automatic flight control and instrument systems. |
| AircraftApproachCategory | Classification of aircraft based on 1.3 times stall speed in landing configuration at certified maximum landing mass. |
| AircraftAddress | A unique combination of twenty-four bits available for assignment to an aircraft for the purpose of air-ground communications, navigation and surveillance. |
| Aircraft | Any machine that can derive support in the atmosphere from the reactions of the air other than the reactions of the air against the earth's surface. |
| AirborneSegment | The airborne segment of the trajectory describes the anticipated 4D path of the aircraft using data elements and resolution necessary to deliver a level of fidelity commensurate with requirements for each portion of the trajectory. |
| AirborneHolding | A tactical ATFM measure requiring aircraft to hold at a waypoint in a predefined standard holding pattern. |
| AIPSupplement | Temporary changes to the information contained in the AIP which are published by means of special pages. |
| AIPAmendment | Permanent changes to the information contained in the AIP. |
| Agreed4DTrajectory | The current 4D trajectory that is agreed between the airspace user and the ASP after collaboration, or imposition of pre-collaborated rules. |
| Agent | Someone who produces or is capable of producing an effect. |
| AerospaceManufacturer | A company or individual involved in the various aspects of designing, building, testing, selling, and maintaining Aircraft, aircraft parts, missiles, rockets, and/or spacecraft. |
| AeroplaneConfiguration | A particular combination of the positions of the moveable elements, such as wing flaps and landing gear, etc. that affect the aerodynamic characteristics of the aeroplane. |
| AeronauticalTelecommunicationNetwork | A global internetwork architecture that allows ground, air-ground and avionic data subnetworks to exchange digital data for the safety of air navigation and for the regular, efficient and economic operation of air traffic services. |
| AeronauticalMeteorologicalStation | A station designated to make observations and meteorological reports for use in international air navigation. |
| AeronauticalInformationService | A service established within the defined area of coverage responsible for the provision of aeronautical information/data necessary for the safety, regularity and efficiency of air navigation. |
| AeronauticalInformationPublication | A publication issued by or with the authority of a State and containing aeronautical information of a lasting character essential to air navigation. |
| AeronauticalInformationCircular | A notice containing information that does not qualify for the origination of a NOTAM or for inclusion in the AIP, but which relates to flight safety, air navigation, technical, administrative or legislative matters. |
| AeronauticalChart | A representation of a portion of the Earth, its culture and relief, specifically designated to meet the requirements of air navigation. |
| AerodromeWarning | Concise information of meteorological conditions which could adversely affect aircraft on the ground, including parked aircraft, and the aerodrome facilities and services. |
| AerodromeTrafficZone | An airspace of defined dimensions established around an aerodrome for the protection of aerodrome traffic. |
| AerodromeSurfaceRoutingNetworkNode | Representation of the intersection of two or more aerodrome features related to taxi operations, or other special location such as holding position or entry or exit to a parking area. |
| AerodromeSurfaceRoutingNetworkEdge | A directional or bi-directional connection between nodes having an attached geometry which can be used for a graphical depiction of the taxi route. |
| AerodromeSurfaceRoutingNetwork | A connected and directed graph defined by Node and Edge features that represents logical and physical connections between taxiways, runways and other features related to the movement area of an aerodrome. |
| AerodromeSign | A sign presenting messages related to aircraft and vehicle movement. |
| AerodromeReferencePoint | The designated geographical location of an aerodrome. |
| AerodromeProtectionArea | An area situated in the vicinity of a runway, Final Approach and Take-Off Area (FATO) or Touchdown and Liftoff Area (TLOF), provided to protect aircraft during manoeuvring, take-off and/or landing operations. |
| AerodromeMeteorologicalOffice | An office, located at an aerodrome, designated to provide meteorological service for international air navigation. |
| AerodromeMarker | An object displayed at an aerodrome above ground level in order to indicate an obstacle or delineate a boundary. |
| AerodromeMappingDatabase | A collection of aerodrome mapping data organized and arranged as a structured data set. |
| AerodromeMappingData | Data collected for the purpose of compiling aerodrome mapping information. |
| AerodromeLocationIndicator | A four-letter code group formulated in accordance with rules prescribed by ICAO and assigned to the aerodrome. |
| AerodromeHotSpot | A location on an aerodrome movement area with a history or potential risk of collision or runway incursion, and where heightened attention by pilots/drivers is necessary. |
| AerodromeElevation | The elevation of the highest point of the landing area. |
| AerodromeControlTower | A unit established to provide air traffic control service to aerodrome traffic. |
| AerodromeControlService | Air traffic control service for aerodrome traffic. |
| Aerodrome | A defined area on land or water (including any buildings, installations and equipment) intended to be used either wholly or in part for the arrival, departure and surface movement of aircraft. |
| AerialWork | An aircraft operation in which an aircraft is used for specialized services such as agriculture, construction, photography, surveying, observation and patrol, search and rescue, aerial advertisement, etc. |
| AerialRefuelling | A procedure used by the military to transfer fuel from one aircraft to another during flight. |
| AdvisoryArea | A designated area within a flight information region where air traffic advisory service is available. |
| AdvisoryAirspace | An airspace of defined dimensions, or designated route, within which air traffic advisory service is available. |
| AcrobaticFlight | Manoeuvres intentionally performed by an aircraft involving an abrupt change in its attitude, an abnormal attitude, or an abnormal variation in speed. |
| Accuracy | A degree of conformance between the estimated or measured value and the true value. |
| AcceptingUnitOrController | Air traffic control unit next to take control of an aircraft. |
| AcceptanceMessage | A message transmitted by an accepting unit to the transferring unit to indicate that the data in a current flight plan or estimate message is accepted. It shall also be transmitted to indicate that the data received in a coordination message is accepted and that the coordination dialogue is completed. |
| AccelerateStopDistanceAvailable | The length of the take-off run available plus the length of the stopway, if provided. |
| 4DTrajectory | A four-dimensional (x, y, z, and time) trajectory of an aircraft from gate-to-gate, at the level of fidelity required for attaining the agreed ATM system performance levels. |