Place a Ping-Pong ball in the stream of air. It stays that way even if you move the hairdryer to an almost horizontal position. Swiss mathematician, discovered a rather strange characteristic of moving air. He found that moving air exerts less pressure in a direction at right angles to its motion than still air does. Airplanes can fly because of this principle.
Air rushing over the tops of airplane wings exerts less pressure than air from under the wings.
So the relatively greater air pressure beneath the wings supplies the upward force, or lift, that enables airplanes to fly.