Hot air balloon technology. The first untethered manned hot air balloon flight was performed by Jean-François Pilâtre de Rozier and François Laurent d'Arlandes on November 21, 1783, in Paris, France, in a balloon created by the Montgolfier brothers. The first hot-air balloon flown in the Americas was launched from the Walnut Street Jail in Philadelphia on January 9, 1793 by the French aeronaut Jean Pierre Blanchard. Hot air balloons that can be propelled through the air rather than simply drifting with the wind are known as thermal airships. Early unmanned hot air balloons were used in China. Zhuge Liang of the Shu Han
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