Authorities in Australia have closed the book on a commercial aircraft that went missing three years ago and has never been found.

In a final report published yesterday, the Australian Transport Safety Bureau (ATSB) said it would be impossible to determine the cause of the disappearance of Malaysia Airlines flight MH370 on March 8, 2014, without finding the remains of the aircraft.

"We...deeply regret that we have not been able to locate the aircraft, nor those 239 souls on board that remain missing," said the report’s authors.

The plane vanished on a flight from Kuala Lumpur to Beijing with 239 people on board. Despite a protracted series of both above and below sea level searches, no debris from MH370 was every found. The report said the underwater searches “eliminated most of the high probability areas,” but they did not enable investigators to pinpoint the location of the wreckage.

China and Malaysia joined Australia in the inquiry into what has become one of the most significant aviation mysteries in history.

The plane is believed to have gone off course and crashed off the coast of Western Australia.

"It is almost inconceivable and certainly societally unacceptable in the modern aviation era ... 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," said the ATSB.