Air Traffic Control [ATC]

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Air traffic control (ATC) is a service provided by ground-based controllers who direct aircraft on the ground and through controlled airspace, and can provide advisory services to aircraft in non-controlled airspace. The primary purpose of ATC worldwide is to prevent collisions, organize and expedite the flow of air traffic, and provide information and other support for pilots. In some countries, ATC plays a security or defensive role, or is operated by the military.

Air traffic control service is a service provided for the purpose of:

  • preventing collisions:
  • between aircraft, and
  • on the manoeuvring area between aircraft and obstructions; and
  • expediting and maintaining an orderly flow of air traffic. (ICAO Annex 11)

Air traffic control service is provided:

  • to all IFR flights in airspace Classes A, B, C, D and E;
  • to all VFR flights in airspace Classes B, C and D;
  • to all special VFR flights;
  • to all aerodrome traffic at controlled aerodromes.

Clearances issued by air traffic control units provide separation:

  • between all flights in airspace Classes A and B;
  • between IFR flights in airspace Classes C, D and E;
  • between IFR flights and VFR flights in airspace Class C;
  • between IFR flights and special VFR flights;
  • between special VFR flights when so prescribed by the appropriate ATS authority,


Further Reading

ICAO Annex 11 Chapter 3 ICAO Doc 4444: Procedures for Air Navigation Services- Air Traffic Management (PANS-ATM)


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