The disappearance of a Malaysia Airlines flight is increasingly baffling, but it is not the first plane to vanish without trace or have its investigation surrounded by confusion and chaos.
From adventurer Steve Fossett's disappearance over the Nevada desert to the claims of a revenge killing behind the crash of EgyptAir Flight 990, here are 10 of the most mysterious aviation disasters.
Surely the most famous plane disappearance of all time belongs to female flying ace Amelia Earhart, whose aircraft disappeared in 1937, during an attempt to circumnavigate the globe. She was flying with her navigator Captain Fred Noonan over the Pacific at the time. After a major search effort failed to find any trace of her or her twin-engine plane, she was declared dead two years later. It has not stopped people looking for her though.
Air France Flight 447
When Air France flight 447 from Rio de Janeiro to Paris went down in 2009, it was five days before any wreckage was spotted and nearly two years before its "black boxes" were found - at a depth of around 4,000m (13,000ft). None of the 228 people on board the Airbus 330 survived. French investigators found that the autopilot disconnected, probably after air speed instruments were frozen by ice crystals, and then the pilots steered the plane at too steep an angle to maintain speed - eventually stalling it - despite a warning sounding in the cockpit for nearly a minute. Air France rejected those accusations.
EgyptAir Flight 990
This routine flight from New York's JFK Airport to Cairo on 31 October 1999 went down in the Atlantic, killing all 217 people on board. Because the crash happened in international waters the investigation fell to Egyptian authorities. After initially asking American aviation officials to investigate on their behalf, Egypt reversed the decision after the US concluded that Egyptian co-pilot Gameel el-Batouty had brought the plane down on purpose. A former EgyptAir pilot suggested a possible motive, claiming that Mr el-Batouty had been reprimanded for sexual misconduct by a company executive who was on the flight. The Egyptian investigation, however, blamed the crash on a mechanical failure.
British South American Airways Star Dust
In August 1947 a British Avro Lancastrian airliner, named Star Dust crashed into a mountain in the Argentine Andes during a routine flight from Buenos Aires to Santiago in Chile. Searches for the aircraft came up blank and conspiracy theories soon emerged that pointed the finger at saboteurs and - after confusion over the final coded transmission to Santiago airport - even aliens. The speculation was eventually put to rest 50 years later when mountaineers stumbled across the remnants of the plane's wreckage and experts concluded that the crew had been confused by poor weather and accidentally started their descent too soon.
Scores of ships and planes are said to have vanished without trace over the decades in this vast triangular area of ocean that has imaginary points in Bermuda, Florida and Puerto Rico. Two British South American Airways planes disappeared in the region in the 1940s, but research by a BBC journalist in 2009 found that one probably suffered a catastrophic technical failure while the other is likely to have run out of fuel. The myth of the Bermuda Triangle, however, lives on.
Uruguayan Air Force Flight 571
Another plane that fell victim to low cloud and high mountains in the days before cockpit technology was able to better inform pilots. Flight 571 was flying from Uruguay to Santiago, Chile, and came down in the Andes, losing both wings as it clipped the top of mountains. Of the 45 people on board the flight, around half survived not only the impact but also a further 72 days stranded on the mountain. Eventually, rescuers reached 16 survivors who admitted they had resorted to cannibalism to stay alive. The survivors' story was told on the big screen in the 1993 film Alive.
TWA flight 800
Trans World Airlines flight 800 left New York's JFK airport shortly after 20:00 on 17 July 1996 and exploded just a few minutes later, killing all 230 people on board. The pilot of another flight radioed Boston air traffic control to say: "We just saw an explosion up ahead of us here...about 16,000 feet or something like that. It just went down into the water." Subsequent investigations blamed the blast on an electrical short circuit that caused an explosion in one of the fuel tanks. Eyewitness accounts spawned several conspiracy theories that, thanks to the growing use of the internet, convinced many that the plane had been shot down. That particular theory gained ground after Pierre Salinger, a journalist who had been President Kennedy's press secretary, claimed that a US missile test had caused the blast but his supporting documents were quickly discredited.
A US Army Air Corps B-24D
An American bomber during World War Two, Lady Be Good went out on a mission over Naples, Italy, in April 1943 and never returned to its base in eastern Libya. At the time it was assumed the plane had crashed in the Mediterranean and its nine-man crew were all designated 'missing in action'. But the plane had in fact overflown its base because of technical issues and carried on for two hours, flying deep into North Africa. Its crew eventually parachuted down to ground and the eight that survived the jump headed north, walking for nearly 100 miles (160 km) before succumbing to the heat and lack of water. The plane was discovered 15 years later, when a British oil exploration team found the wreckage in the middle of the desert. Incredibly, the bomber was remarkably intact and its machine-guns were still functioning.
Steve Fossett's Bellanca Super Decathlon
American adventurer Steve Fossett set off from a private airfield in Nevada on 3 September 2007 never to be seen again. The search for the 63-year-old, who was the first person to fly a plane solo around the world without refuelling, eventually ended when his single-engine plane was found in October 2008 after a massive manhunt involving many agencies, volunteers, and even Google Earth. Investigators said strong winds were the likely cause of the crash.
Private plane carrying fashion boss
A small aircraft carrying the director of Italian fashion house Missoni disappeared off the coast of Venezuela in January 2013. Vittorio Missoni and his wife were among six people on board the flight from the archipelago of Los Roques towards Caracas when it rapidly lost altitude and speed before vanishing from radar. The plane wasn't found until six months after the crash and divers eventually recovered the six bodies, with samples confirming that Mr Missoni and his wife were among them. It was the second time a plane had disappeared in Los Roques and the area has now been dubbed the "new Bermuda Triangle."