The key to keeping an airplane flying is the wings. As the jet engines or propellers move the plane forward, the wing splits the air. Some air flows fast over the wing and the rest flows under it slowly.
Here is where the experts disagree. Some say that the faster flow of air over the wing lowers the air pressure above it. Then the higher pressure of the slow-moving air underneath pushes upward on the wing.
But other scientists say the explanation is simpler than that: the plane flies because the wing is set at an angle that pushes downward on the air.