Overview
Angle of Attack (α, "alpha", AOA) is the angle at which the chord line of the wing meets the relative wind. This means that AOA is also the angle between the chord line and the airplane's flight path. It can be argued that AOA is the most influential determinant of a wing's production of lift.
The critical angle of attack is the AOA at which the wing produces the highest coefficient of lift (CL)— in other words, the wing is producing lift at its maximum efficiency. An increase of AOA beyond this point results in a rapidly decreasing CL. The wing is unable to keep smooth air flow on top of the wing, causing a significant loss of lift. This condition is defined as a stall. It is critically important to note that the only way to recover from a stall is to reduce AOA.