When were civilian aircraft first directed between aerodromes by air traffic control?
In 1920, Croydon Airport, London was the first airport in the world to introduce air traffic control.

In the United States, air traffic control developed three divisions. The first of air mail radio station was created in 1922 after World War I when the U.S. Post Office began using techniques developed by the Army to direct and track the movements of reconnaissance aircraft. 

In 1930, the first radio-equipped control tower in the United States began operating at the Cleveland Municipal Airport. 

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