A Paper Airplane is Designed with Wings
When a paper airplane is designed, the builder folds the sheet of paper to provide maximum wingspan to support the plane for prolonged flight. As with general aviation, paper airplanes may be designed with different wing configurations for speed or lofty, prolonged flight. In addition, some designers choose to add a small weight to the plane to keep it stable in flight.
The Plane Receives Thrust From the Thrower
For any airplane to fly, it must have both thrust and lift. The wings provide lift for the airplane as described in Section 3 below, but the thrust must originate from outside the plane. As with any other form of aviation, the plane's lift overcomes the force of gravity and the plane's thrust must be enough to overcome the laws of inertia. When the paper airplane is thrown, it is thrown with enough force to overcome its tendency to remain still. Some people prefer to throw the plane at a slight upward angle to maximize the amount of time the plane moves forward (using thrust to move slightly upwards and gravity to continue moving). The angle at which the plane should be thrown is dependent on the plane's design.
Wings Carry the Plane Through the Air
As the plane moves forward, its wings cut through the air to generate a small amount of lift. As the air rapidly flows over and under the paper wing, a tiny vacuum is formed over the top of the wing to hold the plane aloft. As the forward motion diminishes, the airflow over the paper wing slows and the lift is reduced. As the thrust and lift subside, a properly designed paper airplane should glide to a safe landing.