Pilots experience different flight characteristics of an airplane when flying very close to the ground, especially noticeable during the landing phase. This phenomenon, known as the ground effect, creates a cushioning effect that makes the airplane seem to float above the ground. The ground effect occurs because an airplane in normal flight, high above the ground, encounters induced drag—a force resulting from lift production. This drag is caused by airflow spilling around the wingtips, over and under the wings, creating a large twisting vortex. This vortex leads to a downward deflection of the relative airflow, tilting the lift vector backwards and generating additional drag.

However, when an airplane flies closer to the ground, the downwash and, consequently, the formation of wingtip vortices are restricted. This restriction means that in ground effect, the lift vector does not tilt back as much, reducing total drag. Consequently, less thrust is required to maintain airspeed. Additionally, the air pressure on the lower wing surface slightly increases in ground effect, generating more lift and contributing to the cushioning sensation pilots feel. Ground effect is most noticeable when the airplane is flying at a height less than half its total wingspan, with the effect strengthening as the wings come closer to the ground.

Ground effect plays a crucial role during takeoff and landing. During takeoff, as the airplane climbs out of the ground effect, its ability to generate lift decreases, and induced drag increases, leading to reduced climb performance. Conversely, when the airplane enters the ground effect on an approach to land, it tends to float longer due to the extra lift and lower drag. Ground effect can also decrease the stalling angle of attack, cause the airspeed indicator to read low, and change the stability characteristics of the airplane when flying closer to the ground surface.