Internationally, the concept of regulated airspace began taking shape after World War I. Under the Treaty of Versailles, the International Commission for Air Na

Internationally, the concept of regulated airspace began taking shape after World War I. Under the Treaty of Versailles, the International Commission for Air Navigation (ICAN) was created in 1919, developing the first air traffic regulatory framework initially signed by 19 states. There is cooperation between states, with the best example I know of being the Maastricht Upper Area Control Centre (MUAC) which was established in 1972 by Eurocontrol and manages the upper airspace (above 24,500 feet) over Belgium, Luxembourg, the Netherlands, and northwest Germany. Eurocontrol is the first and, to the best of my knowledge, the only successful attempt to pool controllers between countries in Europe.