July 30 (UPI) -- In what could be its final word on the matter, the government of Malaysia said Monday it's been unable to reach a definitive conclusion about what happened to a jetliner full of people that vanished four years ago.
Malaysia Airlines Flight 370, or MH370, disappeared March 8, 2014, en route from Beijing to Kuala Lumpur with 239 people aboard. Investigators believe it crashed somewhere in the Indian Ocean, but they've never come up with an explanation or found the plane's wreckage.
"The team is unable to determine the real cause for [Flight 370's] disappearance," the report states.
In its report Monday, the Malaysian government said one thing is for sure -- the Boeing 777 did not deviate from its flight path by accident.
Investigators said it would've been virtually impossible for any system failure to push Flight 370 so far off course. They concluded the plane was almost certainly flown manually to wherever it hit the water.
"The analysis of the relevant aircraft systems ... does not suggest a mechanical problem with the aircraft," the report notes.
The report determined the plane was not on autopilot when it veered off course, meaning someone on the flight deck made it happen.
"The turn back could not be attributed to an anomalous system," Kok Soo Chon, the investigator in charge of the MH370 safety investigation, said at a news conference Monday. "It has been established that the air turn back was done under manual control, not autopilot."
All 239 people aboard the flight are presumed dead.
Although the report didn't come to many definitive conclusions, it did rule out several possibilities, including a theory that one or more of the pilots intentionally crashed the jetliner in an act of suicide.
Other factors ruled out were the mental states of the pilots, mechanical trouble or someone operating the flight systems by remote control.
Authorities, though, said it is possible there was "unlawful interference" by some unknown third party.
Several searches have been mounted for the missing plane over the last four years, but three small chunks of the left wing and tail section found in 2016 are the only pieces of wreckage authorities believe came from MH370.
Authorities previously said Monday's would be the final report on the matter, though officials have since indicated that there could be future updates. Kok said the Malaysian government will reopen the full investigation if the airliner is eventually found.
The Australian government also conducted searches and a full investigation, but its efforts have also turned up few answers.
The report stressed the need for an answer so that similar events can be averted in the future.
"Improvements must be undertaken to ensure that this type of event is identified as soon as possible, and mechanisms are in place to track an aircraft that is not following its filed flight plan for any reason," it said.
"The disappearance of MH370 and the search effort are unprecedented in commercial aviation history."