Air Traffic Control (ATC) is a service provided by ground based controllers who direct aircraft. The primary purpose of ATC is to separate aircraft to prevent collisions either aircraft on ground or in the air, to organize and expedite the flow of traffic and to provide information and other support for aircrews when able. Prevent collisions is refered to as separations, which is a term to prevent aircraft for coming too close to each other by use of lateral, vertical and longitudinal separation minima.

ATC is also provide additional services such as providing information to aircrews, weather and navigation information and NOTAMs (Notice to Airmen).