Here's why:

* Gravity is a fundamental force: It's a force of attraction between any two objects with mass. The more massive the objects, the stronger the gravitational pull.

* Earth's gravity: The Earth has a large mass, creating a strong gravitational field around it. This field pulls on everything near it, including airplanes.

* Counteracting gravity: Airplanes don't fall to the ground because their wings generate lift, a force that pushes them upwards. This lift force is created by the shape of the wings and the way they interact with the air.

* Dynamic equilibrium: While flying, airplanes are in a state of dynamic equilibrium. This means the forces acting on them are balanced. Lift counters gravity, thrust counters drag (air resistance), and the airplane maintains a stable flight.

In essence, gravity pulls airplanes down, but the lift generated by their wings keeps them in the air.