The main point of debate was whether the Malaysian Airlines Boeing 777 hit the sea in an uncontrolled dive or a controlled landing.
If it was controlled that could explain why only a few pieces of debris from the missing plane have ever been found, and could mean it hit the sea outside the area where the search for it has been carried out.
The flight with 12 crew and 227 passengers on board, left Kuala Lumpur early in the morning of March 8, 2014.
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Less than 40 minutes into the flight – around the point where Malaysian air traffic control was to hand over to the Vietnamese – the plane’s transponder and other ground communications were turned off, and the flight disappeared from traffic control screens.
Despite dropping off civilian radar, MH370 was tracked by Malaysian military radar, which showed the plane almost turning around and heading back across the Malaysian mainland.
After Penang, in northwest Malaysia, the plane turned to the northwest, across the Malacca Straits.
Ten days after the plane vanished, UK company Inmarsat reported one of its satellites had picked up a series of faint data signals from aircraft’s engines.
Those signals were meant for the engines’ manufacturer to monitor them in flight, not to show where the plane was, but calculations gave an area where the plane was.
They indicated the plane’s final location was somewhere in an arc that went as far north as Kazakhstan and south deep into the Indian Ocean. A final calculation showed the plane had flown south.
Simon Hardy, one of the panel members and a 777 pilot and instructor, said he believed the plane had initially avoided detection by military radar after turning around by flying along the border between Malaysia and Thailand.
“As the aircraft went across Thailand and Malaysia, it runs down the border, which is wiggling underneath. It means it’s going in and out of those two countries … so both of the controllers aren’t bothered about this mysterious aircraft, because ‘oh. it’s gone, it’s not in our space any more’.”
Hardy said it was “accurate flying” and if he was told to make a 777 disappear he would have done the same thing. At Penang Captain Zaharie Ahmad Shah had dipped his wing to see his hometown. “It might be a long emotional goodbye, or a short emotional goodbye, to his home town.”
Martin Dolan, former head of the Australian Transport Safety Bureau, who led the search for MH370, discounted the possibility the disappearance was carried out by terrorists, saying no one had sought to claim credit for it.
“This was planned, this was deliberate, and it was done over an extended period of time.”
Commenting on why nothing was heard from the plane once it went off course Canadian air crash investigator Larry Vance said: “The thing that gets discussed the most is that at the point where the pilot turned the transponder off that he depressurised the airplane, which would disable the passengers.
“There is no reason not to believe that that’s what the pilot did, because that would be consistent with everything else that the pilot did.”
Had the plane not been depressurised there would have been opportunity for people on the plane to try to make contact with people on the ground. “In my opinion, that’s probably what happened,” Vance said
“He (the pilot) was killing himself. Unfortunately he was killing everyone else on board. He did it deliberately.”
Hardy said he thought someone was controlling the aircraft to the point it hit the ocean. It was “a mission by one of the crew to hide the aircraft as far away from civilisation as possible”.
In an aircraft simulator, shown on the programme, he had pulled out of a so-called death dive. “So now we’re just flying with no engines, we’re just a huge glider,” he said.
In this scenario it took nine minutes to reach the ocean, putting the plane outside the area which had been searched for it.
Dolan wasn’t convinced. “I still think the weight of the evidence … is that for whatever reason, it’s unlikely there were controlled inputs at the end of the flight, and therefore the aircraft spiralled into the water,” he said.
But the ATSB always accepted that there was a possibility the plane was controlled right into the sea.
“If that were the case finding the wreckage would be almost impossible, and with the resources likely to be available “it would be impossible”.
If it was thought a pilot was controlling the plane at the end, the search area would have been different.
Vance said the captain of the flight had wanted the plane to disappear. “The airplane on the bottom of the ocean, as I see it, the fuselage is in one piece, the left wing is still on it, the right wing may be off, the engines are separate. But you basically have four pieces of airplane down there. It’s not scattered all over the bottom of the ocean,” he said.
US air safety expert John Cox said the idea had merit but “this ditching would not be something that would be easily done”.
The 3-4 metres waves in the ocean at the time would have done a lot of damage on the airplane.