A belly landing or gear-up landing occurs when an aircraft lands without its landing gear fully extended and uses its underside, or belly, as its primary landing device.
Normally the term gear-up landing refers to incidents in which the pilot forgets to extend the landing gear, while belly landing refers to incidents where a mechanical malfunction prevents the pilot from extending the landing gear.
During a belly landing, there is normally extensive damage to the airplane. Belly landings carry the risk that the aircraft may flip over, disintegrate, or catch fire if it lands too fast or too hard.
Extreme precision is needed to ensure that the plane lands as straight and level as possible while maintaining enough airspeed to maintain control. Strong crosswinds, low visibility, damage to the airplane, or unresponsive instruments or controls greatly increase the danger of performing a belly landing.
Still, belly landings are one of the most common types of aircraft accidents and are normally not fatal if executed carefully.