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"How Can Planes Fly?”

Simply Science 11

Aeroplanes, or planes, fly due to the principles of aerodynamics, which involve the interaction of various forces acting on the aircraft. The key principles that enable aeroplanes to fly are lift, thrust, gravity, and drag.

Aeroplane in flight seen from the ground

Here's an explanation of how these forces work together to allow flight:


Lift is the force that counters the gravitational pull of the Earth and keeps the aeroplane airborne. It is generated mainly by the wings of the aircraft. The wings are specially designed to have an aerofoil shape, with the upper surface curved and the lower surface relatively flat.

Wing profile:

wing profile

By Olivier Cleynen - Own work, CC0, https://commons.wikimedia.org/w/index.php?curid=16100403

When air flows over the curved upper surface of the wing and the flatter lower surface, it creates a pressure difference. The air pressure above the wing decreases, while the air pressure below the wing remains higher. This pressure difference generates an upward force called lift.


Thrust is the forward force that propels the aeroplane through the air. Thrust is generated by engines. These engines expel high-speed exhaust gases or air backwards, creating an equal and opposite reaction force that pushes the aircraft forward.


The force of gravity pulls the aeroplane downward toward the Earth's surface. To maintain level flight or climb, the lift force must be equal to or greater than the force of gravity. When lift equals gravity, the aeroplane remains at a constant altitude. When lift exceeds gravity, the aeroplane climbs.


Drag is the resistance or friction encountered by the aeroplane as it moves through the air. It opposes the forward motion of the aircraft and is caused by the air's resistance to the aeroplane's shape and movement. Pilots and engineers strive to minimize drag through design and control adjustments to make the aircraft more efficient.

The process of flight involves balancing these forces. During takeoff, the pilot increases engine thrust to overcome the force of gravity. Once enough speed is attained, the lift generated by the wings becomes sufficient to counteract gravity, and the aeroplane becomes airborne. During cruising, the pilot adjusts thrust and control surfaces (like the ailerons, elevators, and rudder) to maintain level flight or climb to a desired altitude.

To descend or land, the pilot reduces engine thrust and may change the wing's angle of attack to increase drag. This allows the aircraft to descend gradually and safely.

As you can see, aeroplanes can fly because of the careful balance of forces, with lift opposing gravity and thrust opposing drag. The design and control of the aircraft, as well as the pilot's skill, all play a role in achieving and maintaining controlled flight.

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