Abstract: There is provided an aircraft position monitoring system for monitoring the position of aircraft in a ground station. An air-borne sub-system mounted in the aircraft acquires, automatically and periodically, monitor data including data on the aircraft position, ID and FOM. The acquired monitor data is transmitted to the ground station via a satellite communication line or a data communication line. In the ground station, the monitor data sent from the aircraft is sent to a monitoring device and a tracking processing unit. The resultant data is displayed on a display device. The tracking processing unit collates the input monitor data with track data in a track file prepared on the basis of flight schedule data of the aircraft, and determines presence/absence of correlation therebetween by referring to FOM data in the monitor data. On the basis of the determination result, the existing track file is updated or a new track file is prepared. Thus, the tracking processing of each aircraft is performed.