The Chicago Convention
By 1944 it was clear that after the war a large number of aircraft and trained crews would be available for civil use, and that countries would have to agree on the rules. In November of that year representatives of 52 states met in Chicago. The convention they signed on 7 December 1944 still forms the basis of international air law.
Its first principle is that every state has complete and exclusive sovereignty over the airspace above its territory. An aircraft of another country may not enter without permission. The convention then sets rules for regular services, for the registration of aircraft and for the safety of flights, and it created an organisation to keep the technical rules consistent, the International Civil Aviation Organization, which began work in 1947 and is now based in Montreal.
The freedoms of the air
Delegates could not agree on commercial rights. Instead they listed a series of “freedoms”, for example the right to fly over another state without landing, the right to land there for fuel, and the right to carry passengers between your own state and another. Which of these a country grants is settled in bilateral agreements, which is why the route map of an airline depends so much on politics.
The technical standards are the quiet success. A pilot trained in one country can read the charts, signs and radio phrases of another, because they follow the same standards.