Air traffic control

Air traffic control (ATC) is a service provided by ground-based air traffic controllers who direct aircraft on the ground and through a given section of 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. Air traffic controllers monitor the location of aircraft in their assigned airspace by radar and communicate with the pilots by radio. To prevent collisions, ATC enforces traffic separation rules, which ensure each aircraft maintains a minimum amount of empty space around it at all times. It is also common for ATC to provide services to all private, military, and commercial aircraft operating within its airspace, not just civilian aircraft. Depending on the type of flight and the class of airspace, ATC may issue instructions that pilots are required to obey, or advisories (known as flight information in some countries) that pilots may, at their discretion, disregard. The pilot in command is the final authority for the safe operation of the aircraft and may, in an emergency, deviate from ATC instructions to the extent required to maintain safe operation of their aircraft. Aeronautical phraseology and Aviation English Pursuant to requirements of the International Civil Aviation Organization (ICAO), ATC operations are conducted either in the English language or the language used by the station on the ground. In practice, the native language for a region is used; however, English must be used upon request. In 1920, Croydon Airport, London, was the first airport in the world to introduce air traffic control. The "aerodrome control tower" was a wooden hut high with windows on all four sides. It was commissioned on February 25, 1920 and provided basic traffic, weather and location information to pilots. In the United States, air traffic control developed three divisions.