The hot air balloon is the first form of human flight. The first documented human flights in a balloon occurred in France in October of 1783. In these flights the balloon was tethered to the ground allowing the balloon to ascend to 80 feet above the ground, the length of the tether. A month later in November of 1783 the first documented non tethered flight occurred in France. The hot air balloon is made up of a bag, called an envelope which holds air that is heated from a basket below. The heated air is less dense then the air around it which makes the balloon buoyant. A valve at the top of the envelope allows the pilot to release hot air which helps to lower the balloon when it is time to land.