The discovery of a piece of debris on the island of Reunion, a French territory in the Indian Ocean, has raised fresh hope that one of aviation’s greatest mysteries may one day be solved.
Here’s what you need to know about the disappearance of Malaysia Airlines Flight MH370.
Where did the plane go missing?
In the early hours on March 8, 2014, Flight MH370 took off from Kuala Lumpur International Airport en route to Beijing, with 239 passengers and crew on board.
At 1:19 a.m. as the Boeing 777-200ER was flying over the South China Sea, Malaysian air traffic controllers radioed the crew to contact controllers in Ho Chi Minh City for the onward flight through Vietnamese airspace.
The crew’s acknowledgment of the request was the last thing ever heard from MH370: “Good night Malaysian three-seven-zero.”
Shortly afterward, air traffic controllers in Malaysia lost contact with the plane somewhere over the sea between Malaysia and Vietnam.
The aircraft’s transponder, which identifies the plane and relays details like altitude and speed to controllers, stopped transmitting. MH370 seemingly disappeared without a trace.
Malaysian authorities revealed later that military radar had tracked the plane as it turned back to the west, flew across the Malay Peninsula, and up the Strait of Malacca, before flying out of radar range at 2.14 a.m. and vanishing once again.
Where did it go?
Planes and ships from a number of countries initially searched areas of the South China Sea, the south of Vietnam and the Malaysian peninsula.
The search area was then expanded into the Andaman Sea, as authorities revealed the plane could have flown for a number of hours after last contact.
A week after the disappearance, Maysian Prime Minister Najib Razak revealed the aircraft was deliberately diverted and had continued flying for more than six hours after losing contact.
Conflicting theories emerged about the plane’s flight path, with speculation about whether it took a “northern arc” or a “southern arc,” and the search area in the southern Indian Ocean changing several times.
After it was determined, through analysis of “handshakes” between the plane and an Inmarsat telecommunications satellite, that MH370 had eventually turned and flown south for hours, searchers focused their attention on a swathe of the Indian Ocean about 2,000 km (1,242 miles) off Australia’s west coast known as the “seventh arc.”
“All the available data indicates the aircraft entered the sea close to a long but narrow arc of the southern Indian Ocean,” the Australian Transport Safety Bureau says on its website.
Australia has taken the lead in the search and recovery operation in support of the Malaysian accident investigation since March 31, 2014.
False leads
The discovery of a piece of debris on the island of Reunion is the biggest lead in the case in a very long time.
But hopes were raised several weeks after the aircraft’s disappearance, when a commercial satellite and then a Chinese satellite made sightings of large objects in the southern Indian Ocean that Australian and Chinese authorities believed could be debris from the aircraft.
The sightings led nowhere.
Not long after, there was optimism that searchers had made a breakthrough when four acoustic “pings” were detected in an area of the southern Indian Ocean on April 5 and 8.
Officials expressed “cautious optimism” at the faint noises. But after seven weeks focusing their efforts around the area where the sounds were heard, searchers discounted the notion that the pings had come from the missing plane’s black boxes.
Conflicting theories
In the absence of any firm answers, competing theories have surfaced as to what led to the plane’s mysterious disappearance along a circuitous flight route.
One theory is that one of the pilots may have incapacitated the other, then deliberately taken the plane down in an act of pilot murder-suicide — a nightmarish scenario that would subsequently become a reality in the Germanwings crash of March 2015.
Some have suggested that a guest in the cockpit could have commandeered or hijacked the plane, although the lack of any claim of responsibility makes this less likely. While others argue a more conventional explanation, such as mechanical failure, is more likely.