---Malaysia Airlines Flight MH370
Malaysian Airlines flight MH370 disappeared at 17:30 GMT Friday (01:30 local time Saturday) en route from Kuala Lumpur to Beijing. It reportedly disappeared from radar screens south of Vietnam. Malaysia Airlines had previously said it last had contact with air traffic controllers 120 nautical miles off the east coast of the Malaysian town of Kota Bharu.

Malaysian officials have said that radar signals suggest the plane may have turned back. The air and sea rescue teams that have been searching an area of the South China Sea south of Vietnam for more than 24 hours have now expanded their search to land on the west coast of Malaysia.

Air safety experts are investigating whether the Boeing 777 could have been the target of a terrorist attack. Malaysia's transport minister, Hishammuddin Hussein, said two names on the passenger list were "suspect". The passengers using stolen passports – one Italian and one Austrian – were both booked on the same onward flight from Beijing to Amsterdam on Saturday.


---Trans World Airlines (TWA) Flight 800
Trans World Airlines (TWA) Flight 800 crashed off the coast of East Moriches, Long Island, on 17 July 1996 en route from JFK International Airport to Paris, France, killing all 230 people on board in the United States' second-deadliest plane crash.

After a four-year investigation the official verdict was that the crash was caused by a fuel tank explosion due to a spark from a damaged wire. But not everyone believes that, and the producers of a documentary that aired in 2013 argued that the plane was shot down. FBI investigators said they found explosive residue on the plane, which may have indicated a terrorist attack. Several witnesses said they saw the plane being shot down by one or even two missiles, possibly during a naval training exercise gone wrong. The documentary argued the truth was covered up either by the US Government or by the air industry, which might otherwise have faced billions of dollars in financial losses.


---Aerolinee Itavia Flight 870
Aerolinee Itavia Flight 870 was a domestic Italian commercial flight en route from Bologna to Palermo when it crashed into the Tyrrhenian Sea between Ponza and Ustica, killing all on board in 1980.

The disaster led to numerous investigations, legal actions and accusations, and continues to be a source of speculation, including claims of conspiracy by the Italian government and others. Former Italian President Francesco Cossiga officially attributed the cause of the crash to a missile fired from a French Navy aircraft.

The conspiracy theories that sprang up after the official verdict included a terrorist attack, a missile strike during a Nato training exercise and that the plane was shot down by a missile in a strike against Libyan forces. In the months and years after the crash seven Italian air officials who were involved in the investigation died in suspicious circumstances including car crashes, murders and suicides.


---Pan Am flight 103
One of the most famous plane crash conspiracies of recent years involved Pan Am Flight 103, the transatlantic flight from Frankfurt to Detroit via London and New York City that was destroyed by a terrorist bomb on Wednesday, 21 December 1988 over the Scottish town of Lockerbie. All 243 passengers and 16 crew on board died, and 11 people on the ground were killed by falling debris.

Following a three-year investigation, arrest warrants were issued for two Libyan nationals in November 1991. Former Libyan leader Colonel Muammar Gaddafi eventually handed them over for arrest after protracted negotiations and UN sanctions. In 2001, Libyan intelligence officer Abdelbaset al-Megrahi was jailed for the bombing. In August 2009, he was released by the Scottish government on compassionate grounds after being diagnosed with prostate cancer. He died nearly three years later.

In the years that followed numerous conspiracies developed regardingthe destruction of Pan Am Flight 103. Gaddafi maintained he never ordered an attack on the plane. But in 2011, during the Libyan civil war, a former government official contradicted Gaddafi and claimed that the Libyan leader had personally ordered the bombing. A report commissioned by President George Bush suggested that the bombing had been a case of state-sponsored terrorism.


---Air France Flight 1611
Air France Flight 1611 was en route from the island of Corsica to Nice on 11 September 1968 when it crashed into the Mediterranean off Nice, killing all 95 on board including French army general René Cogny. According to the official report, the crash was non-survivable. The crash remains the highest death toll of any aviation incident in the Mediterranean. At the time the probable cause was attributed to a fire that originated in the rear of the cabin.

But a radio programme broadcast by BBC Radio 4 in November 2007 put forward a conspiracy theory that the accident was the result of a missile strike or bomb, and that the true cause has been suppressed by the French Government under secrecy laws. On 10 May 2011 Michel Laty, a former military secretary, declared on French television channel TF1 that a missile, misfired by the French army during a weapon test, had caused the crash.


---Korean Air Lines Flight 007
Korean Air Lines Flight 007 was a scheduled flight from New York City to Seoul via Anchorage on 1 September 1983. But the aircraft flew through prohibited Soviet airspace around the time of a US reconnaissance mission and the plane was shot down by a Soviet Su-15 interceptor near Moneron Island in the Sea of Japan. All 269 passengers and crew aboard were killed, including Lawrence McDonald, a sitting member of the United States Congress.

The Soviet Union initially denied knowledge of the incident, but later admitted shooting down the plane, claiming that the aircraft was on a spying mission. The USSR government said it was a deliberate provocation by the United States to test the Soviet Union's military preparedness, or even to provoke a war. The Soviet military suppressed evidence sought by the International Civil Aviation Organization (ICAO) investigation, notably the flight data recorders, which were eventually released eight years later after the collapse of the Soviet Union. This prompted a number of conspiracy theories during the Cold War.


---9/11 Al-Qaida attacks
Four passenger airliners were hijacked by 19 al-Qaida terrorists on a suicide missions. Two of those planes, American Airlines Flight 11 and United Airlines Flight 175, crashed into the North and South towers, respectively, of the World Trade Center complex in New York City. A third plane, American Airlines Flight 77, crashed into the Pentagon, the headquarters of the United States Department of Defense.

The terrorists had intended to crash the fourth plane, United Airlines Flight 93, over Washington, DC but crashed into a field near Shanksville, Pennsylvania, after its passengers overpowered the hijackers. In total, almost 3,000 people died in the attacks, including the 227 civilians and 19 hijackers aboard the four planes.

Many 9/11 conspiracy theories surfaced shortly after the 11 September attacks. Theorists believe that the World Trade Center buildings were demolished by bombs, phone calls from the planes were made up, and that former President George W Bush secretly profited from the attacks.


---The Bermuda Triangle mysteries
Scores of ships and planes are said to have vanished without trace in the Bermuda Triangle – a vast triangular area of ocean with imaginary points in Bermuda, Florida and Puerto Rico.

Among the unsolved mysteries, on 30 January 1948, a BSAA Avro Tudor IV plane disappeared without trace. Twenty-five passengers and a crew of six were on board The Star Tiger. No bodies or wreckage were found. The official investigation into the disappearance concluded: "It may truly be said that no more baffling problem has ever been presented. What happened in this case will never be known and the fate of Star Tiger must remain an unsolved mystery."

Almost a year after the disappearance of the Star Tiger, another Avro Tudor IV belonging to BSAA vanished between Bermuda and Jamaica. Exactly one hour after departure from Bermuda on 17 January 1949, the pilot of the Star Ariel sent a routine communication of his position. But then the plane vanished without trace at 18,000 feet. According to experts, this would have required a sudden catastrophe. Again, no wreckage, debris or bodies were ever found. Fuel starvation at that height was not plausible, the weather report had been good, and pilot error was ruled out.


---Amelia Earhart's circumnavigation of the globe
Amelia Mary Earhart, the American aviation pioneer and the first female aviator to fly solo across the Atlantic Ocean, disappeared on 2 July 1937 while attempting to fly around the world in a Lockheed Model 10 Electra. Its last known point was over the central Pacific Ocean near Howland Island. Fascination with her life, career and disappearance continues to this day.

The two main theories are that Earhart's plane either crashed and sank over Howland Island, or that she ran out of fuel and landed on uninhabited Gardner Island, now Nikumaroro, part of the Phoenix Islands in the Republic of Kiritbati in the western Pacific Ocean, and perished.

There are scores of conspiracy theories surrounding Earhart's disappearance, including that she not only survived the flight, but returned to America to live out her days under an assumed name.

However, in July 2013, TIGHAR (The International Group for Historic Aircraft Recovery) sonar detected an object on the seabed near Nikumaroro which it identified as a Lockheed Electra, the type of plane Earhart was flying. Past expeditions in the area have discovered 1930s beauty cream, a woman's compact, and buttons and zipper from a flight jacket. TIGHAR will return to the island later this year to inspect the wreckage and perhaps conduct a dig.