Angle of Attack

The angle of attack is the tilt between the wing and the oncoming air. Increase it and you deflect more air downward, generating more lift. Pilots adjust this constantly — more angle for slow speeds, less at cruise.

But past roughly 15-20 degrees, airflow cannot follow the wing's surface. It separates, turbulence replaces smooth flow, and lift collapses. This is a stall — the wing has not stopped moving, but it has stopped flying.