Commanders look out the cockpit windows during search operations for missing Malaysia Airlines Flight MH370 in Southern Indian Ocean, near Australia.

Australia has ended its search for the missing MH370 Malaysia Airlines flight that disappeared three years ago carrying 239 people.

The country's civil aviation authority admitted in its final report that it was no closer to discovering what happened after the plane was lost during a scheduled flight from Kuala Lumpur to Beijing.

Australian searchers said reasons for the loss of MH370 would never be known until the aircraft is found.

"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 Australian Transport Safety Bureau (ATSB) said on Tuesday.

The report's summary ended with a message to families related to the missing people.

"The ATSB expresses our deepest sympathies to the families of the passengers and crew on board MH370. 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," the report added.