# Angle of attack

## Explanation

Angle of attack is the angle between the chord line of an airfoil and the relative direction of the aircraft. This angle is the key factor of an airfoil to generate lift. The lift coefficient of an airfoil increases up to the critical angle of attack. Beyond the critical angle, the lift coefficient drops abruptly due to the flow separation on the upper surface of the wing, eventually causing the airfoil to stall. The angle of attack is denoted by the symbol alpha (α).