1. Local Control: These are the controllers in the tower. Their responsibility is to safely guide aircraft from the gate to the runway and vice versa. They also control aircraft within the airports aerodrome which is usually 2-5 miles away from the airport who are planning to land at the airport or have just departed from the airport.
2. Terminal Radar Approach Control (TRACON): Many airports have a radar control facility that is associated with the airport. While every airport varies, terminal controllers usually handle traffic in a 30 to 50 nautical mile (56 to 93 km) radius from the airport. Where there are many busy airports in close proximity, one single terminal control may service all the airports. The actual airspace boundaries and altitudes assigned to a terminal control are based on factors such as traffic flows, neighboring airports and terrain, and vary widely from airport to airport.
Traffic flow is broadly divided into departures, arrivals, and overflights. As aircraft move in and out of the terminal airspace, they are handed off to the next appropriate control facility (a control tower, an en-route control facility, or a bordering terminal or approach control). Terminal control is responsible for ensuring that aircraft are at an appropriate altitude when they are handed off, and that aircraft arrive at a suitable rate for landing.
3. EnRoute Control or "Center" Control: These controllers maintain radar separation for aircraft that are enroute to their destination. Their airspace is typically above the TRACON's airspace in the higher altitudes, and in areas where there is not a TRACON, they provide separation for aircraft going to smaller airports that aren't controlled by a TRACON.
So, in plain English. Let's pretend your on a flight. You board the aircraft and listen to that totally interesting safety briefing. Behind the scene this is what is happening: The pilots request for clearance to the airplanes destination, they are cleared through clearance delivery and then handed off to ground control. The ground controller (in the tower) safely gets the plane from the gate to just short of the runway and then hands the plane off to the tower controller (who is also in the tower, duh). The tower controller give permission for the plane to take off, ensuring the runway is clear of traffic. After take-off you are handed off to the TRACON as you climb to your cruise altitude until you leave the TRACON's airspace and are handed off to the Center Controllers. By this time you are enjoying your sprites, cokes, and various airliner accoutrement. You cruise for a while under Center control until you begin to descend into your destination. Once you are within a specified altitude and range from your destination you are handed off back to the TRACON. This is when you are descending and making numerous turns to satisfy aircraft separation and also to place you into the arrival sequence. The TRACON controller places you on final approach and hands you off to the Tower controller. They issue clearance to land, you land, taxi to the gate, and then play watch the bags come down the ramp game until yours shows up (hopefully).
There it is folks, it was a long post, but it could have been much longer. I just wanted to give a perspective of what air traffic controllers do while you're in the air. It's quite a symphony of airplanes! Follow my blog to watch me go from zero experience, to earning the trust of fellow controllers so I can be part of the symphony's conduction. Stay tuned, it all starts November 4th.
