Most air traffic controllers today do their jobs without ever seeing the aircraft they guide. They monitor radar screens to track aircraft. As aircraft fly over radar sites, the data from those radars is communicated digitally via telecommunications lines to controllers hundreds or even thousands of miles away.
Controllers in en route facilities guide airplanes flying at high altitudes through large sections of airspace. As aircraft fly across the country, pilots talk to controllers in successive en route centers. There are 21 en route centers that control aircraft flying through Unites States airspace.
At approach control facilities, controllers guide aircraft as they approach, or leave, airspace surrounding airports to about 40 miles away.
Controllers at most of these facilities handle approach control for many different airports in one facility. For example, Potomac TRACON handles air traffic going into and out of all the airports around Washington D.C., Baltimore, MD, and Richmond, VA. All of the controllers in this facility are experts at one section of the airspace the facility controls, but they work closely together to ensure a smooth transition of all aircraft though the entire region.
At the Air Traffic Control System Command Center, controllers plan air traffic for the entire country, taking into consideration how weather and other events, such as military maneuvers, will affect air traffic patterns. Command Center controllers talk to controllers in other facilities and to airline traffic managers to come up with “master plans.”
The public is most familiar with air traffic control towers at airports. Controllers in these facilities guide aircraft as they take off or land and taxi from or to the gate. Their primary function is to separate aircraft on the airport surface. But many airports in the United States don’t have towers so controllers at remote approach control facilities guide aircraft into and out of those airports.