Flight may seem complicated, but in fact it's based on some simple laws of nature. The principle of lift When you examine a cross-section of an airplane's wing, or airfoil, you'll notice that the top part is curved and the bottom part is relatively flat. This special shape creates lift, which makes the airplane fly. As the wing moves forward, the air flowing over the top travels faster than the air flowing beneath, resulting in a lower pressure area above the wing. The relative pressure differential provides the upward force called lift.
Lift is basic to flying.
In order for an airplane to climb, lift must be greater than gravity, the force that holds objects on the earth. For an airplane to maintain level flight at a particular altitude, lift and gravity must be the same, or in equilibrium. When gravity is greater than lift, the airplane will descend. An airplane, of course, is more than a wing, a propeller and an engine. The body of the airplane, which holds the pilot, passengers, and baggage, is called the fuselage.