How do planes fly?

A big airplane can weigh hundreds of tons and yet it rises into the air and crosses oceans. How is that possible? To fly, a plane needs four forces working together: thrust, lift, weight and drag.

Thrust: moving forward

The engines push the plane forward, either with propellers or with jet engines that blow air out at high speed. Without moving forward there is no flight, because air has to flow over the wings.

Lift: going up

Wings have a special shape: they are more curved on top than underneath and slightly tilted. When air flows past them at high speed, the plane receives an upward force called lift. The faster it goes, the more lift; when lift is bigger than the weight, the plane takes off.

Weight and drag: what holds it back

Weight is the force with which gravity pulls the plane toward the ground. Drag is the friction with the air, which tries to slow it down. That is why planes have long, smooth shapes: to cut through the air easily.

Takeoff, flight and landing

To take off, the plane speeds down the runway until it is fast enough for the wings to hold it up. In the air, pilots move the ailerons, the rudder and other moving parts to turn, climb or descend. When landing they slow down, lower panels called flaps so the wings can keep holding the plane at a lower speed, and the brakes do the rest.

Experiment: a paper plane

Make two paper planes: one with flat wings and another with the back edges folded slightly upward. Throw them with the same strength and measure which one flies farther. Change the weight with a paper clip and test again. You are doing what engineers do: checking how shape and weight affect flight.

Something to think about

Birds use lift too: when they glide with open wings they use the air flowing past them. The first airplane inventors were inspired, in part, by watching how birds fly.

💡 A big airplane weighs hundreds of tons and still flies.