There are some basic mechanics that allow an airplane to fly. These mechanics are four primary forces which everyone is familiar with in some way, without even realizing it.

lift

Lift it the force that actually makes an airplane fly, or "lifts" it off the ground. When the air passes over a wing, it creates a partial vacuum on the upper surface of the airfoil, because the air has to travel faster than the bottom surface of the wing. Since a high pressure area always moves toward a low presure area, the wing is forced upward. Related Links: Propulsion

gravity

Gravity is the force that pulls us downward, toward the earth. This force counteracts lift, and the balance of the two forces allow an airplane to maintain a constant altitude while in flight.

thrust

This force moves the plane forward, causing air to flow over the wings, thus producing lift. It can be produced with a propeller, which is nothing more than a set or sets of wings that are spun by an engine. The same principle that causes the wings to produce lift enable the propeller to move the airplane forward.

drag

Drag is the force that counteracts thrust. Also known as wind resistance, the balance of drag and thrust allow the plane to maintain a constant speed while in flight. Related links: See how it flies, by John Denker