<em>Answer:</em>
Thrust and Lift.
<em>Method:</em>
There are 4 forces acting upon a plane while it is moving. Drag (The air friction while it's in the air), Lift (Generated by the wings (The upward force), Weight (How heavy the plane is), and finally, Thrust (Generated by the engines which moves the plane/wings through the air generating lift). If there is enough air going over the wing at a high enough speed, and Thrust, and Lift overcome the other two forces keeping the plane on the ground, it can fly. The air pressure under the wing is higher than over the wing - If you have ever ran you hand under the water keeping it flat, you may notice it going up, those are basically the same forces, but under water.
How does the pressure under the wing affect the lift?
The difference of air pressure over the wing (which is less), which also means less force bringing the plane down. The air pressure under the wing is higher, putting pressure on the wing moving it up. A wing is designed to make the air travel a longer distance over the wing than under the wing creating the air pressure. The engines just enforce that process.
