Nowadays, international flights are nothing out of the ordinary. Yet ensuring that airlines can fly into the sovereign airspace of other countries requires international agreements. The first binding international accord to secure air travel rights was signed in 1944: the Convention on International Civil Aviation, or the Chicago Convention for short. Its first article states that every state has complete and exclusive sovereignty over airspace above its territory. Should an airline wish to offer a route from its home country to another country, it requires further authorizations from the states concerned. To make sure international air traffic proceeds smoothly in such cases, there are nine “freedoms of the air.”: