How is a stall defined in aviation terms?

In aviation, a stall specifically refers to a condition in which the aircraft exceeds its critical angle of attack. At this angle, airflow begins to separate from the wing's upper surface, which drastically reduces lift. This is a fundamental concept in aerodynamics, as the performance of the wing significantly deteriorates once the critical angle is surpassed. During a stall, the aircraft may lose altitude and responsiveness, making it crucial for pilots to recognize and recover from this condition promptly. Understanding this definition is essential for safe flight operations, as it helps pilots anticipate the risks associated with flying at high angles of attack, particularly in low-speed scenarios.

The other definitions do not accurately capture the essence of a stall. A sudden increase in engine thrust does not relate to the stall condition, nor does prolonged flight at low speed, which can occur without stalling. Engine failure during flight, while critical, is not a stall but a separate issue concerning power loss in flight.