Tony Abbott said the search for missing MH370 flight should continue, as he claims the tragedy was probably the result of a pilot "murder-suicide".

The former Australian prime minister spoke out as the three year anniversary beckons next weekend to mark the disappearance of the Boeing 777.

No real trace of the airplane carrying 239 passengers has ever been found, except for a flaperon, which was discovered on the French island of Réunion on 29 July 2015 that was "determined to have been a part of the MH370 aircraft", according to an interim report by Malaysia's Ministry of Transport last year.

Grieving families' hopes were further dashed when the official 120,000sq km search for the plane in the southern Indian Ocean was suspended in January.

But Abbott, now a backbencher, still believes the search for the doomed airliner should continue in areas which have not yet been explored.

"There's absolutely no doubt that while there is any, any reasonable prospective places to search we should still be searching, no doubt about that in my mind," he told News Corp Australia, according to a report by Adelaide's The Advertiser.

"I have always said the most plausible scenario was murder-suicide and if this guy wanted to create the world's greatest mystery, why wouldn't he have piloted the thing to the very end and gone further south? Then there was the analyses that suggested there might be a prospective place to the north.

"When you've got nearly 240 people missing, the greatest mystery of modern times, as long as there is any reasonable prospective place to search you just keep searching."

Captain Zaharie Ahmad Shah was originally at the centre of the FBI probe after allegations emerged he purposely veered the plane off course while on its way to Beijing. Investigators were asked to help recover deleted files from a flight simulator the pilot used.

It was only in August 2016 when Malaysian officials admitted for the first time that data from Shah's flight simulator at his home in Kuala Lumpur included a flight path to the southern Indian Ocean.

Malaysian transport minister Liow Tiong Lai told the local press shortly afterwards: "Until today [6 August 2016] this theory is still under investigation. There is no evidence to prove that Captain Zaharie flew the plane into the southern Indian Ocean.

"Yes, there is the simulator but the (route) was one of thousands to many parts of the world. We cannot just base on that to confirm (he did it)."

It was alleged he was having marital problems with wife Faizah Hanun. Although the couple still lived together in Kuala Lumpur they had reportedly separated.

She refused to reveal any details about her husband's thoughts and behaviour leading up to him piloting the plane.

But what she has told investigators is understood to have been an important factor in the interim conclusions to be released about the airline's fate, which are still yet to be released.

Meanwhile, a group, voice370, acting on behalf of grieving families, will be arranging a day of remembrance at The Square at Publika, Kuala Lumpur.