Stall break is the behavior of an aircraft when it reaches stall speed. Wings with varying airfoil profile stall progressively, that is to say, parts of the wings stall before others, which keep flying. For a tapered, delta wing aircraft such as a hang glider, the root of the wing stalls first, progressing outboard to the tips. Because the wingtips are aft of the nose of the hang glider, the lift they produce when the root stalls causes the aircraft to try to rotate more nose-down and resume flying properly. This action is called the stall break.

A stall break can be sharp and distinct or it can be a gradual increase in nose-down force. Higher performance gliders generally are allowed to have sharper stall breaks than are acceptable on beginner wings, since the pilots flying high performance wings are expected to be ready and able to deal with such behavior. The severity of a stall break is somewhat dependent on angle of attack and the rate at which one slows from flying to stall. One can get even the most docile glider to do a sharp stall break by picking up speed and then rapidly pushing the nose up and holding it until stall. This is known as a "whipstall" and is a common way to initiate a high-speed dive in preparation for aerobatic maneuvers, such as loops and wingovers. A whipstall can easily lead to loss of control of the glider and is generally best avoided.

Since hang gliders are usually flown as slowly as possible in lift (i.e. minimum sink speed) to get the best climb rate, a sharp stall break can mean that small errors in speed control are costly in terms of altitude and efficiency. In rough air, one's airspeed and angle of attack frequently change abruptly and by several miles per hour in either direction, so a sharp stall break is a major liability, and even dangerous if one is flying near others or close to the terrain.