What makes things fly?

Answer 1

Airplanes exploit a loophole in the physics of air pressure. It's a mundane sort of thing, compared to being IN a plane, but essentially, air gets bottlenecked trying to go around an airfoil (such as the wing of a plane) and more ends up being pushed up, into the wing from below, rather than flowing over it smoothly. Helicopters use their rotors to pull air down in a column, like a ceiling fan. They almost ride the column of air like a man climbing a rope. Hot-air-balloons heat air in a sealed environment and rise because hot air is less dense than cold air.

Answer 2

Things fly when the lift force generated by their wings or propellers overcomes the force of gravity pulling them down. This lift force is created by the movement of air around the object, resulting in upward movement. Additionally, thrust from engines or other propulsion systems can also contribute to flying by providing forward motion.