Wind shear is a change in wind speed and/or direction in a short distance. It can exist in a horizontal or vertical direction and occasionally both. It is typically associated with thunderstorms and low-level temperature inversions, but can also be caused by the jet stream and weather fronts.

—A shear from a tailwind to a headwind causes the airspeed to increase and the nose to pitch up with a corresponding balloon above the glide path.

—A shear from a headwind to a tailwind has the opposite effect, and the aircraft will sink below the glide path.

—A headwind shear followed by a tailwind shear is particularly dangerous because the pilot has reduced power and lowered the nose in response to the headwind shear.