short takeoff and landing aircraft (STOL), heavier-than-air craft, capable of rising from and descending to the ground with only a short length of runway, but incapable of doing so vertically. The precise definition of an STOL aircraft has not been universally agreed upon. However, it has been tentatively defined as an aircraft that upon taking off needs only 1,000 ft (305 m) of runway to clear a 50-ft (15-m) obstacle at the end of that distance and upon landing can clear the same obstacle and then land within 1,000 ft. Typically, STOL aircraft have large wings that are equipped with special aerodynamic devices such as slotted flaps, drooped leading edges, and auxiliary spoilers that augment lift, increase stability, and improve the effect of control surfaces. As the airfields from which STOL planes are expected to operate will be in confined areas, the ability to fly stably at low speeds, especially in turbulent air, is an important design requirement for them. See vertical takeoff and landing aircraft.