Malaysia and Australia say they remain “hopeful” that flight MH370 will eventually be found, two years on from its disappearance.
The aircraft disappeared between Kuala Lumpur and Beijing on 8 March 2014 with 239 people on board.
Australian-led search teams are combing a 120,000 sq km (46,330 sq mile) area of the southern Indian Ocean.
Only one confirmed piece of debris, a part of wing called a flaperon, has been found, on Reunion Island.
The search, involving Australian, Chinese and Malaysian experts, is estimated to have cost more than $130m (£92m).
The countries have said it will end once the current search area has been completely covered, likely to be around June.
In a statement on Tuesday, Malaysian Prime Minister Najib Razak said he remained “hopeful that MH370 will be found”, but once the search zone is exhausted the three governments would meet to determine the way forward.
“We remain committed to doing everything within our means to solving what is an agonising mystery for the loved ones of those who were lost,” he said.
But Martin Dolan, head of the Australian Transport Safety Bureau (ATSB) which is co-ordinating the search, told the BBC the governments’ positions were unchanged and the search would end then, “unless new and significant information comes to light”.
Many relatives want the operation to continue until the plane is found.
Australian Transport Minister Darren Chester also expressed hope on the anniversary, saying finding the plane would “give answers to the world, in particular the families of missing loved ones, about what happened”.
On Monday, relatives of 12 Chinese passengers filed lawsuits in Beijing.
Lawyer Zhang Qihuai said they were seeking a range of damages, but their goal was to determine the cause of the accident and those who were responsible.
Families of 32 other passengers, mostly Chinese, have filed a separate lawsuit in Malaysia, and in the US, 43 passengers’ relatives have sued in New York.
There are believed to be a number of other cases under way around the world.
Under international agreements, relatives have two years following an air accident to begin legal action.
Last year, authorities found a piece of wing on the shore of Reunion island in the Indian Ocean. It was later confirmed to be a flaperon from the missing plane.
A second suspected piece of debris was found last week in Mozambique.
It will be analysed by in Australia by the ATSB, along with representatives of the plane’s manufacturer Boeing and the Malaysian investigation team advising.
Although a long way from the suggested possible crash area, both finds are consistent with prevailing ocean currents that could carry debris across the Indian Ocean.
An interim report into the search will be released by Malaysian investigators on Tuesday.