8.2 Air Traffic Control Entities

On any given day there are about 50,000 aircraft flying through the skies. That is about 5,000 aircraft in the sky every hour. Keeping all of these aircraft from certain catastrophic collisions are Air Traffic Controllers. Air Traffic Controllers direct aircraft movement to keep them safe. (Freudenrich) Usually when you think about Air Traffic Controllers you imagine them sitting high up in the tower at airports.  That is not always the case. The Tower manages departures and landings as well as ground maneuvers to and from the gates as well as to and from the runways, but most controllers cannot physically see the aircraft. (Navair)

Approach and Departure Controllers, or Area Control, are typically located in the lower level of the tower. They will take over control of the aircraft from the tower after the aircraft departs. They will also take control from Air Traffic Control – Center for arrivals. Much like Area Controllers, Air Traffic Control Center, cannot physically see the aircraft either. There are 21 zones divided up throughout the United States that are labeled as “Center”. Center will watch the movement of the aircraft throughout the zones and will pass aircraft from zone to zone as the aircraft passes through the airspace. Each aircraft is typically monitored by one or more air traffic controller from center. As the aircraft closes in on their destination, center will then pass the aircraft to the area controller, who will then assist them with the final approach information for landing and pass them back to tower. (Freudenrich)  

References:

Freudenrich, Craig. How Stuff Works. How Air Traffic Control Works. Retrieved from https://science.howstuffworks.com/transport/flight/modern/air-traffic-control.htm

Naviair. Basic information. Retrieved from http://www.naviair.dk/air-traffic-control.1236.aspx