Ed Yost own interests turned toward reviving the lost practice of manned hot-air ballooning. This technology had first been invented in France by in the late 18th century by pioneers led by the Montgolfier brothers, but under the Montgolfier system, the balloon's air was heated by a ground fire prior to the balloon being released. The inherent danger of this type of balloon flight led to the system being abandoned when hydrogen and later helium became available. One of Yost's key engineering insights was that a hot-air balloon could be made to carry its own fuel. The invention of relatively light burners
Hot air ballooning forecasts. The pilot will also send up a helium pilot balloon, known as a "met-balloon" in the UK and "pibal" in the USA, prior to launch to get information about what the wind is actually doing. Another way to determine actual wind directions is to watch other hot air balloons, which are the equivalent of a large "met-balloon". The direction of flight depends on the wind, but the altitude of the balloon can be controlled by changing the temperature of the air inside the envelope. The pilot may open one or more burner blast valves to increase the temperature inside