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.