In 1921, Croydon Airport, London was the first airport in the world to introduce air traffic control.[3]
In America, Air Traffic Control developed three divisions. The first - Air Mail Radio Stations (AMRS) was created in 1922 after World War 1 when the US Post Office began using techniques developed by the Army to direct and track the movements of reconnaissance aircraft. Over time the AMRS morphed into Flight Service Stations. Today's Flight Service Stations do not issue control instructions, but provide pilots with many other flight related informational services. They do relay control instructions from ATC in areas where Flight Service is the only facility with radio or phone coverage. The first Airport Traffic Control Tower, regulating arrivals, departures and surface movement of aircraft at a specific airport, opened in Cleveland in 1930. Approach/Departure Control facilities were created after adoption of RADAR in the 1950s to monitor and control the busy airspace around larger airports. The first Air Route Traffic Control Center, which directs the movement of aircraft between departure and destination was opened in Newark, NJ in 1935, followed in 1936 by Chicago and Cleveland.