The air traffic capacity of two-dimensional airspace

At the present day European ATC is exercised by a multiplicity of more-or-less autonomous control centres. ‘Flow Regulation’ is used roughly to match traffic demand to the capacity of the en-route ATC and of the destination airport. The ATC authority at the point of departure for a remote destination cannot however give any guarantee that the pilot will be able to follow his chosen trajectory. The filed flight plan and the departure clearance have been described as a ‘licence to get into the sky and see what happens’. The present paper will describe a preliminary quantitative study of a population of traffic in random flight. This was intended to give some experience of the modelling problems whilst postponing the task of establishing a detailed forecast of traffic in an area. The model is in two-dimensional space, in which the traffic units are separated from each other only in the horizontal plane. It could therefore represent traffic cruising at a given flight level, or any other airspace where vertical separation between aircraft is not guaranteed. It has been designed to permit its expansion to depict problems in 3-dimensional space.