In January, the governments of Malaysia, Australia and China called off the search for the plane -- which disappeared en route from Kuala Lumpur to Beijing in March 2014 -- after more than 1,000 days of scouring a more than 710,000 square kilometer patch of the Indian Ocean.
"The reasons for the loss of MH370 cannot be established with certainty until the aircraft is found," the Australian Transport Safety Bureau (ATSB) said Tuesday in its final report on MH370.
"It is almost inconceivable and certainly societally unacceptable in the modern aviation era with 10 million passengers boarding commercial aircraft every day, for a large commercial aircraft to be missing and for the world not to know with certainty what became of the aircraft and those on board."
The new report exhaustively documents the efforts taken to find the plane, including a huge, years-long multi-country underwater search.
"The ATSB expresses our deepest sympathies to the families of the passengers and crew on board MH370," the report said.
"We share your profound and prolonged grief, and deeply regret that we have not been able to locate the aircraft, nor those 239 souls on board that remain missing."
Greatest aviation mystery?
MH370 departed from Kuala Lumpur in the early morning of March 8, 2014 heading towards Beijing on a routine journey. Within hours it had stopped communicating, then vanished from radar after it made an unexpected turn to the west.
There were 227 passengers and 12 crew on board when it disappeared.
It has never been confirmed what happened to the aircraft after that, although the search for the plane has centered on the seas off the western coast of Australia.
Debris confirmed to be from the missing aircraft has washed up along the eastern coast of Africa and the beaches of Indian Ocean islands on multiple occasions since the plane went missing.
In addition, analysis of the last satellite readings from the missing plane showed it was spiraling fast towards the sea
when it stopped transmitting.
While the official search was called off in January 2017, relatives of the missing passengers, who were mainly Chinese, have refused to give up on the missing airliner and have said they are planning to continue the search through a private company.
In Tuesday's report, investigators said understanding of MH370's location is "better now than it has ever been." But ultimately it has not been good enough.
The Australian government has said only "credible" new evidence will cause the search to be resumed.