100 years of air traffic control
While the precise date for the founding of air traffic control services remains in dispute, the period of 1920-1922 is when ATC began.
During the 1920s, airplanes like this Airco DH.4 bomber, designed by Geoffrey de Havilland, were pressed into airline service, in this case for flights between London Croydon Airport to Paris. At that time, air traffic control consisted of red and green lights for takeoff.