The Greatest Mystery MH370 ,Do You Remember ?

MALAYSIA Airlines flight MH370 became the world's greatest aviation mystery when it disappeared without a trace.

Four years on, experts are no closer to finding the missing Boeing 777. Here's what we know.

Malaysia Airlines Flight MH370 took off from Kuala Lumpur and was heading to Beijing with 239 people on board.

Passengers included Chinese calligraphers, a couple on their way home to their young sons after a long-delayed honeymoon and a construction worker who hadn't been home in a year.

But at 12.14am on March 8, 2014, Malaysia Airlines lost contact with MH370 close to Phuket island in the Strait of Malacca.

Before that, Malaysian authorities believe the last words heard from the plane, from either the pilot or co-pilot, was "Good night Malaysian three seven zero".

The Malaysian government is releasing the findings of what it says will be its final probe on Monday

Experts over the years have offered a number of theories as to what happened to the plane, ranging from a mechanical defect to an intentional murder-suicide by the captain.

Oxygen deficiency: The Malaysian government and the Australian Transport Safety Bureau took the theory that passengers and flight crew — including Captain Zaharie Ahmad Shah — fell unconscious due to an oxygen deficiency. One version of this theory suggests the oxygen supply was deliberately hacked.

Pilot’s murder-suicide: InMay this year, a team of aviation specialists on 60 Minutes came to the conclusion that Capt Zaharie downed the aircraft in an act of murder-suicide, having plotted a flight plan to nowhere on his home simulator.

Suggested reasons for doing this range from rumours that his marriage was in trouble, to a political protest against then-Malaysian opposition leader Anwar Ibrahim, as a way to destabilise the corrupt government of Najib Razak.

In May this year, a team of aviation experts slammed the murder-suicide theory as “absurd”.

Remote takeover: Earlier this year, Malaysia’s former Prime Minister Tun Dr Mahathir Mohamad suggested a remote takeover took place to counter a hijacking attempt.

“The capacity to do that is there,” he said in March.

“The technology is there. You know how good people are now with operating planes without pilots. Even fighter planes are to be without pilots.

“Some technology we can read in the press but many of military significance is not published.”

Chinese terror group: A shadowy group called the Chinese Martyrs’ Brigade claimed responsibility for the disappearance of MH370 just days after the plane vanished — but officials were sceptical and said the claim could be a hoax.

The previously unheard of group sent an email to journalists across China that read: “You kill one of our clan, we will kill 100 of you as pay back.”

But the message provided no details of what brought the flight down.

Suspicious passengers: In another theory, suspicions fell upon a pair of Iranian nationals who boarded the flight with fake passports.

"But authorities concluded it was unlikely that either man had terrorist links or had anything to do with the plane’s disappearance.