(PD) Photo: Jon Sullivan
Hot air balloons in flight.
Hot air balloons are the most popular type of buoyant aircraft.
Hot air balloons were the first type of aircraft to carry humans. The first one
was built by the Montgofier brothers and flown in Paris in 1783.
Hot air balloons are distinct from gas balloons in that their buoyancy is
obtained by heating air, typically with a propane burner, rather than
using an unheated gas such as Helium.