How come an airplane floats in air?

Answer 1

Essentially there are 4 aerodynamic forces that act on an airplane in flight; these are lift, drag, thrust and gravity (or weight).

In simple terms, drag is the resistance of air (the backward force), thrust is the power of the airplane's engine (the forward force), lift is the upward force and gravity is the downward force. So for airplanes to fly, the thrust must be greater than the drag and the lift must be greater than the gravity (so as you can see, drag opposes thrust and lift opposes gravity).

This is certainly the case when an airplane takes off or climbs. However, when it is in straight and level flight the opposing forces of lift and gravity are balanced. During a descent, gravity exceeds lift and to slow an airplane drag has to overcome thrust.