A wing is shaped and tilted so the air moving over it moves
faster than the air moving under it. As air speeds up, its
pressure goes down. So the faster-moving air above exerts less
pressure on the wing than the slower-moving air below. The
result is an upward push on the wing--lift!
Many factors affect the amount of lift a wing creates: the
size and shape of the wing, the angle at which it meets the
oncoming air, the speed at which it moves through the air, even
the density of the air.