Safety is the most important job of the FAA. The FAA ensures that aircraft are safe to fly, that pilots and mechanics are qualified, and that the people and systems that regulate the flow of air traffic do so safely.
One big part of safety is making sure that planes don't run into each other when they are in the air. The National Airspace System (NAS) is a complex system made up of the people, equipment and systems that monitor every plane in the air over the United States and large parts of the world's oceans at any given moment. The NAS oversees both U.S. civilian and commercial aviation and provides traffic control for military craft flying over domestic airspace. This is a huge task - according to the FAA, an average of 50,000 flights use the NAS each day. In 2006, the Air Route Traffic Control Centers (ARTCCs) routed more than 46 million flights [source: FAA Administrator's Fact Book].
When an aircraft is at an airport, it is managed by an airport traffic control tower (ATCT). The ATCT is located at the airport and handles the departures and arrivals of aircraft at that particular airport. Large airports, such as Dallas-Fort Worth, may have more than one ATCT due to their size and volume of traffic.
Once the plane has departed and is five miles from the airport, the ATCT hands it off to local terminal radar approach control (TRACON) facilities. A TRACON is normally the "middleman," managing the airspace around major metropolitan areas, generally within a 30- to 50-mile radius and under 10,000 feet [source: FAA TRACON fact sheet]. Once the aircraft leaves that zone, the plane enters what the FAA calls "en route airspace," and the TRACON hands the aircraft off to the regional ARTCC. However, if the aircraft is small and stays below 10,000 feet throughout the flight, the TRACON handles the entire flight.
ARTCCs are the heart of airspace management. There are 22 ARTCCs, each of which is responsible for an area of airspace defined by the FAA. Next, we'll learn how ARTCCs operate.