Young Red Haired Girl With Ballons

Balloons are often deliberately released, creating a so-called balloon rocket or rocket balloon. Rocket balloons work because the elastic balloons contract on the air within them, and so when the mouth of the balloon is left open, the gas within the balloon shoots out, and, due to Newton's third law of motion, the balloon is propelled forward. This is the same way that a rocket works.
• Flying machines
Large balloons filled with hot air or buoyant gas (often hydrogen or helium) have been used as flying machines since the 18th century. The earliest flights were made with hot air balloons using air heated with a flame, or hydrogen; later, helium was used. Unlike an airship, a balloon travels with the wind.