The number of aircraft in the airspace is increasing every year. Nowadays airlines are constantly overloaded. The little altitude deviation can lead to a conflict situation between airplanes. Modern airborne collision avoidance systems (ACAS) are unable to operate in the congested airspace. The system generates a new flight trajectory for the both involved airplanes if ACAS reveals a potential conflict. This flight trajectory might produce new conflict situations with other aircraft within congested airspace. Air traffic controllers (ATC) and pilots work under high psychological pressure. Therefore the flight safety level is reduced. This problem is very actual today.
Every air navigation parameter of flight has some deviation from its real valuations. It is the result of some errors influencing. Every measurement device introduces errors of measurement as well. These errors depend on operation life of measuring equipment. The real flight trajectory usually differs from the flight-planned trajectory. It might be the result of pilot’s mistakes as well. The summary of all these errors produces a very significant deviation from the flight-planned trajectory and the conflict situation between the airplanes as the result. Therefore the purpose of modern navigation equipment is to control position of an aircraft in the congested airspace.
Multiple-choice classification can be used for the real-flight trajectory observation. This classification shows a pilot and ATC the class of air situation. Each class depends on deviation value from the flight-planned trajectory