An emergency landing is a landing made by an aircraft in response to a crisis which either interferes with the operation of the aircraft or involves sudden medical emergencies necessitating diversion to the nearest airport.
There are several different types of emergency landings for powered aircraft: planned landing or unplanned landing
If there is no engine power available during a forced landing, a fixed-wing aircraft glides, while a rotary winged aircraft (helicopter) autorotates to the ground by trading altitude for airspeed to maintain control. Pilots often practice "simulated forced landings", in which an engine failure is simulated and the pilot has to get the aircraft on the ground safely, by selecting a landing area and then gliding the aircraft at its best gliding speed.
If there is a suitable landing spot within the aircraft's gliding or autorotation distance, an unplanned landing will often result in no injuries or significant damage to the aircraft, since powered aircraft generally use little or no power when they are landing. Light aircraft can often land safely on fields, roads, or gravel river banks (or on the water, if they are float-equipped); but medium and heavy aircraft generally require long, prepared runway surfaces because of their heavier weight and higher landing speeds. Glider pilots routinely land away from their base and so most cross-country pilots are in current practice.
Since 2003, research has been conducted on enabling UAVs to perform a forced landing autonomously.
Large airliners have multiple engines and redundant systems, so forced landings are extremely rare for them, but some notable ones have occurred. A famous example is the Gimli Glider, an Air Canada Boeing 767 that ran out of fuel and glided to a safe landing in Gimli, Manitoba, Canada on July 23, 1983. On June 1982, British Airways Flight 9, a Boeing 747 en route from Kuala Lumpur to Perth flew into a plume of volcanic ash and lost power in all four engines, three of which subsequently recovered, eventually diverting to Jakarta. On April 28, 1988, Aloha Airlines Flight 243 experienced an explosive decompression when approximately 35 square-meters of aluminium skin separated from the fuselage. The flight was successfully diverted to Kahului Airport with only one casualty, flight attendant Clarabelle "C.B." Lansing who was sucked out when the cabin depressurized. Less than a month later, another 737, TACA Flight 110, lost both engines due to bad weather but was able to land safely on a grass levee on the grounds of NASA's Michoud Assembly Facility outside New Orleans. One year later, United Airlines Flight 811, a Boeing 747, suffered a cargo door failure in-flight, separating a section of fuselage with 9 passengers and resulted in cabin depressurization. The plane made a successful emergency landing at Honolulu International Airport. More recently, Air Transat Flight 236 ran out of fuel over the Atlantic Ocean on August 24, 2001 and made a successful forced landing in the Azores. On November 1, 2011 a Boeing 767 LOT Polish Airlines Flight 016 made a belly landing after a central hydraulic system failure at Warsaw, Poland's Frederic Chopin International Airport, with no injuries.