The main concern of air traffic controllers is safety. They keep track of planes flying within their assigned area and make certain that planes are a safe distance apart. They also try to coordinate the movement of planes in a way that reduces delays. Controllers keep track of several aircraft at once and need to make certain that each pilot receives correct instructions. Air traffic controllers regulate traffic between or within airports.
Tower controllers are responsible for monitoring aircraft around an airport.
They visually watch aircraft as they move. The job of tower controllers is to keep airplanes a safe distance apart as they land or take off. En route controllers monitor planes as they fly from one airport to another. These controllers cannot see the airplanes, so they rely on blips on a radar screen to tell them where the planes are. Air traffic controllers use two-way radios to give clearance give traffic information.