A plane's movement — from preflight checks made at the gate through landing at a destination airport — is closely coordinated by a series of air traffic controllers at the origin airport, in the region, along the plane’s route and at the destination airport. Each has a specific duty in the process, and is vital to the efficiency of air travel. How air traffic control works:
Preflight: Weather information is obtained and a flight plan is filed. The airport's air traffic control tower gives the plane a route clearance to fly, and it pushes back from the gate. The tower tells the pilot which taxiways to use in preparation for takeoff.
Takeoff: The local tower controller gives the plane clearance for takeoff.
Departure: After the plane is five miles beyond the airport, the control of the plane is transferred to a Terminal Radar Approach facility, or TRACON. There are 185 TRACONs in the U.S., including one in Elgin, that covers O’Hare and Midway. During this phase, the aircraft is routed away from the airport via an assigned route and altitude.
4. In the air: Oversight is handed off to an Air Route Traffic Control Center, or ARTCC, a radar facility overseeing flights passing through its zone. The Chicago Center covers parts of seven states. Controllers monitor the flight and give instructions to the pilot as the aircraft passes through the center’s airspace, from sector to sector.
5. Descent: When the plane is within about 50 miles from its destination airport, it is handed to the destination's TRACON controller.
6. Approach: The TRACON controller then blends several streams of descending aircraft into one evenly paced, smooth-flowing line of aircraft lined up for a particular runway.
7. Landing: The flight is handed off to the local controller stationed at the destination airport's control tower. This local controller issues clearance for landing. The aircraft lands and is handed off to the ground controller, who directs the pilot across the taxiways to the destination gate.