However, they were not ruling out any possibility since the in-air turn back was done manually and the systems in the plane were also manually turned off.
An independent investigation report into Malaysia Airlines Flight 370 says the cause of the plane's disappearance still can not be determined and the "possibility of intervention by a third party can not be excluded".
It said the cause of the disappearance still can not be determined and the "possibility of intervention by a third party can not be excluded".
It said it could not exclude the interference of a third party, but concluded it was unable to determine the real cause of the disappearance.
"It is possible that the absence of communications prior to the flight path diversion was due to the systems being manually turned off, whether by intent or otherwise", he said at a news conference, adding the report wasn't final and conclusive given the wreckage wasn't found.
The MH370 story is etched in aviation history as the most weird incident, how a Boeing 777 with 239 people onboard vanished under mysterious circumstances, unleashing never ending scenarios provided both by aviation experts and conspiracy theorists.
The investigation had been described as a "final report", but in his opening remarks Kok said, "This is not a final report".
"We can not establish if the aircraft was flown by anyone other than the pilot", he said.
There was a 2.4-ton shipment of lithium ion batteries on board that had not been scanned because there were no X-ray machines big enough, as well as 4.5 tons of mangosteen fruit.
He, however, hoped the government would consider resuming the search.More news: West Brom offered encouragement in chase for Newcastle United striker
One area that came in for criticism in the report by the 19-member investigation team, which included foreign investigators, was air traffic control.
The disappearance of the flight has become the world's greatest aviation mystery.
Malaysia called off its search for MH370 on May 29.
Police didn't find any data that showed a similar route flown by Flight 370 and concluded that there were "no unusual activities other than game-related flight simulations", Kok said. But that search was called off after failing to find anything.
It was the second major search, after Australia, China and Malaysia ended a fruitless AUS$200m (£112.8m) search across an area of 120,000 square kilometres (46,332 square miles) past year.
The only confirmed traces of the aircraft have been three wing fragments washed up along the Indian Ocean coasts. What prompted Captain Zaharie Ahmad Shah or anyone else onboard to turn back the plane and veer off to the Southern Indian Ocean without indicating the reasons or distress to the ATC remains unanswered in the report released today.
She said the meeting between relatives and officials descended into a "shouting match" as anger mounted.
Overall the safety investigators found most fault with the air traffic controllers, first in Kuala Lumpur and then Ho Chi Minh City, who were meant to be watching the plane but who had not followed protocol, meaning the plane was off radar for about 20 minutes before anyone was alerted.
There have been a host of theories about why the plane disappeared, ranging from an accident to a hijacking or even a terror plot.