Families devastated by the loss of flight MH370 vowed Sunday never to quit fighting for answers in the aviation mystery and said the huge search for the Malaysia Airlines plane should continue until something is found.

Families gathered for a poignant ceremony in Kuala Lumpur ahead of Tuesday's second anniversary of the jet's disappearance and to argue for an expansion of the search if the current area being scoured comes up empty.

"We are fighting to search on because our loved ones are not home yet. So how can we say it's the end?" said Jacquita Gonzales, wife of flight steward Patrick Gomes.

The unprecedented Australian-led hunt for wreckage from the Boeing 777 is expected to finish its high-tech scanning of a designated swathe of seafloor in the remote Indian Ocean by July.

Australian, Malaysian and Chinese authorities plan to end the search -- projected to cost up to $130 million -- at that point if no compelling new leads emerge.

A piece of the plane washed up on the French-held island of La Reunion last year, and new debris that is yet to be confirmed as from MH370 was found on a Mozambique beach last week.

But the finds came thousands of kilometres from the suspected crash zone and have yielded no clues.

In one of aviation's greatest enigmas, the plane inexplicably vanished during an overnight flight from Kuala Lumpur to Beijing, carrying 239 passengers and crew.

- 'OK, what next?' -

Citing imprecise satellite data, search authorities believe it flew for hours to the remote southern Indian Ocean and went down.

Many relatives remain unconvinced that authorities are searching in the right place.

"If they have exhausted one particular line of inquiry, that doesn't mean other areas may not come up with something. Just sit down and ask, 'OK, what next'?" said K.S. Narendran, an Indian national whose wife Chandrika was aboard.

Authorities hope to detect debris far down in the ocean depths and eventually recover and analyse the black boxes for clues.

Martin Dolan, chief commissioner of the Australian Transport Safety Bureau (ATSB) and head of the challenging operation, told AFP last week he remained "very hopeful" something can be found before the 120,000-square-kilometre (46,000-square-mile) search zone is fully scanned.

Many next-of-kin accuse the airline and Malaysian government of letting the plane slip away through a bungled response and covering up what caused the disappearance.

Some also allege Malaysia wants to stop searching to prevent embarrassing information from emerging, which the airline and government strongly deny.

Sunday's ceremony included prayers, musical performances and the release of 240 white balloons, one for each passenger and another for the plane.

Relatives say acceptance of their unexplained loss remains impossible two years on.

"We don't have anything to accept. We still know nothing and we are all in limbo. If anything I am worse than before," said Grace Nathan, a Malaysian attorney who lost her mother.

Added Gonzales: "We will fight on to make sure that we get the truth of exactly what happened to all of them. We will not give up."

Australia search team still 'hopeful' as MH370 hunt nears end
Sydney (AFP) March 4, 2016 - Australian authorities say they are not ready to declare defeat in the hunt for missing plane MH370 and remain "very hopeful" of finding it despite the clock ticking on the massive search effort.

The hunt in the treacherous southern Indian Ocean -- where the Malaysia Airlines jet is believed to have come down on March 8, 2014 -- involves sophisticated ships and equipment and is projected to cost up to Aus$180 million (US$130 million).

But it has so far drawn a blank as the two-year anniversary of the mystery disappearance nears.

Only a two-metre-long (almost seven-foot) flaperon wing part that washed up on a Indian Ocean island beach last July has been confirmed as from the aircraft, although suspected debris found in Mozambique this week could be another breakthrough.

The latest find will be brought to Australia for examination, with Transport Minister Darren Chester saying its location was consistent with drift modelling based on the plane crashing in the area being probed.

Australia's search chief Martin Dolan said he still held out hope of finding MH370 as an end to the difficult underwater hunt edges closer with the scouring of more than 85,000 (32,818 square miles) of a designated 120,000 square kilometres zone complete.

"We haven't yet located the aircraft but we have a considerable area still to cover -- over 30,000 square kilometres -- still to go," Dolan, chief commissioner of the Australian Transport Safety Bureau (ATSB) told AFP.

"So we remain very hopeful that we will find the aircraft."

The plane, which disappeared after inexplicably diverting from its planned Kuala Lumpur-Beijing route, had mostly Chinese, Malaysian and Australian passengers on board.

Those three governments have agreed that when the target area is fully searched, expected around June to July, they will pull the plug unless "credible new information" emerges.

Relatives of MH370 passengers have issued an emotional plea to keep searching beyond July, with one group representing the families begging authorities not to "simply chalk it up as an unsolvable mystery".

- 'Searching in right place' -

Despite the search having turned up nothing other than some long-lost shipwrecks, Dolan said he remained confident it was looking in the right place.

The area being scoured, off Western Australia, was identified using analysis of where the plane was calculated to last emit a satellite "handshake" and how the jet went down.

Analysis points to it entering the water within the so-called seventh arc, with investigators saying the "most likely" scenario was that no-one was at the controls and the plane ran out of fuel.

Some critics have questioned why authorities do not give greater weight to the "rogue pilot" theory that someone was at the controls.

Dolan said investigators considered all scenarios -- including the "very unlikely" possibilities the jet was ditched under engine power or was glided into the water by someone after it ran out of fuel -- and presented them to the three governments.

But the alternative possibilities and their potential debris fields would involve an area three times the current search zone.

"There's always been that uncertainty, which is why we've said we're working with probability, we say it is very probable that the aircraft is in our search area, but it's not certain.

"They (the governments) are aware of the potential other scenarios but they are saying that 120,000 square kilometres is the most that's practicable for governments and for us."

If nothing turns up in the remaining stretches of seabed, Dolan said it was "very unlikely that any significant new evidence will come to light", meaning the search will end.

Analysis of the flaperon has so far not offered further information to help solve what happened to the plane.

"The main piece of missing evidence to solve this mystery is the aircraft itself, which is why we've focused so much effort on the search and on finding it," said Dolan. "And I can't see where alternative information is likely to come from."