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The International Air Transport Agreement of December 1944 defined the five "freedoms of the air" (where the following definitions relate to aircraft registered in state A):
1st freedom - the right to fly over state B without commercial or technical stops.
2nd freedom - the right to land in state B for technical purposes, e.g. refuelling.
3rd freedom - the right to set down traffic from state A in state B.
4th freedom - the right to pick up traffic in state B destined for state A.
5th freedom - the right to pick up traffic in state B destined for state C or put down traffic in state B originating in state C.
In addition, other "freedoms of the air" are often referred to. Although not formally defined, these are commonly understood as follows:
6th freedom - a service taking passengers between states B and C which flies via state A.
7th freedom - a service between state B and state C operated by airline of state A (also called a "free-standing fifth freedom").
8th freedom - cabotage, picking up and setting down traffic within the borders of state B by an aircraft registered in state A.