Key 1:
The airport tower controls the aircraft on the ground before takeoff and then about 5 miles from the tower, when the tower transfers aircraft control to a terminal Radar Approach Control facility (TRACON). Controllers I the airport tower either watch the aircraft without technical aids or use radar Airport Surface Detection Equipment for aircraft on the surface and airport surveillance radar for those in the air. Central Flow Control can order the tower to hold flights on the ground id demand exceeds capacity at the arrival airport.
Key 2:
The TRACON which may be located in the same building as the airport tower, controls aircraft from about 15 miles to about 30 miles from the airport, using aircraft position information from the aircraft surveillance radar. The TRACON the transfers control to an Air Route Traffic Control Center (ARTCC).
Key 3:
ARTCCs control aircraft that are en route between departure and arrival airports. Each ARTCC controls a specific region of airspace and control is handed off from one ARTCC to another when a boundary is crossed. Aircraft positions are detected by the air route to an Air Route Traffic Control Center (ARTCC).
Key 4:
The TRACON controls the arriving aircraft until it is within about 5 miles of the arrival airport tower, when control is transferred to the tower.
Key 5:
The airport tower controls the aircraft on the final portion of its approach to the airport and while it is on the ground.
