How do planes stay in the air?

Flatten your hand, angle it up a little, and very carefully hold it outside the window of a moving car, you'll feel a force pushing it upwards. The force is lift and it keeps planes in the air.

When you hold your hand out of the car window, it pushes the flowing air down. So the air pushes back up with on equal and opposite force. Your hand is also pushing forward, and that's matched by an equal and opposite force pushing it back that is drag.

The power to generate lift comes from a plane's engines. Jet engines suck in masses of air and squirt it out the back, pushing the plane forwards. The forwards motion makes air travel.

So next time you go on a plane look it the wing. You can see the wind coming up on top and you might appreciate how flight works....