When an airplane flies above you, you see its shadow because of the way light travels. Light is a form of energy that travels in waves. When these waves hit an object, they are either reflected (bounced off the object) or absorbed (taken in by the object). The color of an object depends on which wavelengths of light it absorbs and which wavelengths of light it reflects.

In the case of an airplane, the metal surface of the plane reflects most of the light that hits it. This reflected light is what you see when you look at an airplane. However, some of the light that hits the plane is not reflected. Instead, it is absorbed by the plane's surface. This absorbed light is converted into heat, which causes the plane to become warmer.

The shadow of an airplane is caused by the part of the plane that blocks the light from reaching your eyes. When an airplane flies above you, the part of the plane that is between you and the sun blocks the sunlight from reaching your eyes. This creates a shadow on the ground.

The size and shape of an airplane's shadow depend on a number of factors, including the size and shape of the plane, the angle of the sun, and the distance between the plane and the ground.

Airplane shadows can be seen on clear days and at night. However, they are most visible on clear days when the sun is shining brightly.