Weight's opposing force is lift, which retains an airplane in the air. This feat is accomplished via the use of a wing, also called an airfoil. Such as drag, lift can exist only in the existence of a moving fluid.
It does not matter if the object is stationary and the fluid is moving (as with a kite on a windy day) or if the fluid is still and the object is moving via it (as with a soaring jet on a windless day). What really matters is the relative difference in speeds among the fluid and the object.
As for that actual mechanics of lift, the force takes place when a moving fluid is deflected with a solid object. The wing splits the air flow in two directions: down along the underside of the wing and up and over the wing.
Whenever an airplane moves into the wind, the wings reduce the airflow in half. Some air moves above the wing, some air moves below the wing.
Plane wings are develop to be curved on top and flat on the base. The air stream or wind, flowing over the wing moves a different path through air traveling below the wing. This difference in the path of the wind, produces lower air pressure above the wing. The higher air pressure beneath the wing lifts the plane into the air making lift. When there is sufficient lift to overcome gravity, the plane takes off.
All the time, the airplane is being slowed up by having to push via the air. This is known as drag and the motors have to overcome it. As long as the plane carries on to move forward at a fast enough pace, the plane continues to fly.
Beginning with simple kites, humans have moved on to develop gliders, airships, helicopters, commercial planes and even supersonic flight.
While birds have been flying for millions of years, it's something relatively new to humans and we rely on some important scientific principles to achieve it.
Disturbed air and friction create drag as the plane moves forward, slowing it down.
Supersonic flight (breaking the sound barrier) is achieved when an object travels at a speed faster than sound (1235kph, 768mph).
The only living things capable of powered flight are insects, birds and bats.
An engine provides thrust to move the plane forward at a speed great enough to overcome drag and allow the wings to create the lift necessary to fly.
Flying fish have been known to glide for hundreds of metres thanks to enlarged fins that act like wings.While some can glide, bats are the only mammals that can achieve sustained level flight.