A hot air balloon is a lighter than air aircraft consisting of a bag called the envelope that is capable of containing heated air. Suspended beneath is a wicker basket, which carries passengers, propane tanks and open flames burner. For modern sport balloons, the envelope is generally made from nylon and Nomex. The heated air inside the envelope has less density than external air, so the balloon can fly under buoyancy force. The hot air balloon is the first successful human-carrying flight technology. The first untethered manned hot air balloon flight was performed in 1783 in a balloon created by the Montgolfier brothers.