Lots of things that go up into the air can't stay there, such as a ball you toss to your friend, because gravity pulls the object back down. Airplanes, however, are different: They’re built in a special way that allows them to stay up so they don't come back down to the ground until they’re ready to land!
When it comes to flight, four different forces try to pull an airplane in opposite directions. A plane is able to fly when its upward and forward pulls are able to be stronger than its downward and backward pulls!
The forward pull of a plane comes from its engine, which gives it power to move. In order to fly, one thing a plane must do is have more forward push from its engine than the backward push it receives from the air in front of it. (It’s sort of like how you might have to push hard with lots of energy to walk forwards into wind pushing against you.)
The other important part of the equation in how airplanes fly is, of course, being able to lift upwards into the air! The upward lift of a plane is created thanks to the special curved shape of a plane’s wings. The way air flows over and under the curved wing is what allows a plane to lift up, up, up! Planes are able to stay in the air because they have more upwards lift than the natural downward pull of gravity! – FLIGHT!