CANBERRA, Oct. 3 (Xinhua) -- The Australian Transport Safety Bureau (ATSB) expressed regret on Tuesday that the search for Malaysian Airlines flight MH370 had been unsuccessful, saying it wished it could have delivered better news to bereaving friends and families of those missing.

In releasing the ATSB's final report on Tuesday, bureau Chief Commissioner Greg Hood offered his condolences to the family and friends of those 239 passengers and crew who were lost with the flight, an incident he described as "a great tragedy."

"We wish that we could have brought complete closure to the bereaved," Hood said in a media release accompanying the publication of the ATSB's "Operational Search for MH370" report.

"I hope, however, that they can take some solace in the fact that we did all we could do to find answers. Governments from around the world contributed to the search, with extraordinary expertise committed to the task.

"Our deepest sympathies remain with those who lost loved ones on MH370... it remains a great tragedy.

"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 flight disappeared in March 2014 en route from Kuala Lumpur to Beijing.

Hood praised the international collaboration involved in the search which became the largest of its kind in aviation history. The initial search zone was 60,000 square kilometers but was doubled in April 2015. The recovery effort was suspended in January 2017, after more than two-and-a-half years.

"This was an unprecedented endeavour and there has been an extraordinary response from the global community," he said.

"There were contributions of expertise and resources from private business and organizations, agencies from different governments, and from private individuals.

"The search inspired dedication from so many. I am proud to have worked with people of such commitment."

The governments of Australia, Malaysia and China agreed that the ATSB was best-suited to lead the search for the plane due to the search taking place in the Southern Indian Ocean off the coast of Western Australia.

"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 ATSB's report said.