The year 2022 marks the 100th anniversary of air traffic control
After extensive research, we propose 1922 as the year in which air traffic control began in earnest.
The first internationally agreed rules, drafted in 1919 by the Commission Internationale de Navigation Aérienne (CINA), were ratified by 10 countries in 1922.
The first mid-air collision between two commercial airliners over Normandy (France) in April 1922 further encouraged the UK, France, Belgium and The Netherlands to implement guidelines for keeping aircraft separated, thus forming the basis for air traffic control as a service to avoid collisions.
The route between Croydon, UK and Le Bourget (France) quickly gained popularity as flying could save a considerable amount of time compared to a ferry crossing. Both airports recruited controllers and erected dedicated structures that were the precursors of an ATC tower. Both countries started employing controllers around that time (1921-22).
At Croydon, these controllers began issuing take-off 'clearances' from July 1922. Around the same time, they began coordinating flights between the different observation posts along routes and between airports.
As the route network expanded, so did the need for Air Traffic Control.