Relatives of 12 Chinese passengers of the missing Malaysia Airlines flight MH370 have filed lawsuits in Beijing, one day before the deadline for launching legal action.
They say they want the courts to help establish what happened to the plane.
Families of 32 other passengers, mostly Chinese, filed a separate lawsuit in Malaysia, their lawyer has said.
MH370 disappeared on 8 March 2014 while flying from Kuala Lumpur to Beijing with 239 people on board.
Under international agreements, relatives have two years following an air accident to begin legal action.
Zhang Qihuai, the lawyer for the 12 families, said they were seeking a range of damages, but their goal was to determine the cause of the accident and those who were responsible.
The total compensation requested from Malaysia Airlines, Boeing, engine manufacturer Rolls Royce and insurance companies ranged between 10m and 70m yuan ($1.5m to $10.8m; £1m to £7.6m) per family, Mr Qihuai was quoted by AFP news agency as saying.
Verdicts might not come for two years, he said.
The companies have not commented.
Many relatives were crying as they presented their documents to court officials. Some said they hoped to use the action to obtain more information about the case.
"Today we came to demand our people back. We come every day. We demand to have our people back everyday, we want our relatives," Dai Shuqin, whose sister was on board the flight, told the Reuters news agency.
In Kuala Lumpur, lawyer Ganesan Nethi said he filed a joint lawsuit on behalf of the relatives of 32 passengers last Thursday. He said most were Chinese, along with one American and a few Indians, AP reported.
The lawsuit named the airline, the Malaysian government and its air force and civil aviation department, he said.
It was not immediately clear how many lawsuits have been filed in total or how many cases have been settled in relation to MH370.
Ships in the Indian Ocean are still searching for the missing Boeing 777, in an operation that is estimated to have cost more than $130m (£92m).
Meanwhile, Mozambican civil aviation officials handed over suspected debris from the missing flight to Malaysian experts.
If confirmed, the object found by an American amateur investigator would be the second piece of known debris from the aircraft to be found.
Piece of suspected aircraft wreckage that was found on the Mozambican coastlineLast year authorities found a piece of the plane's wing on the shore of Reunion island in the Indian Ocean.
The debris could provide fresh clues to the mystery of the flight. Based on satellite communications data, MH370 is thought to have crashed in the Indian Ocean.
"Currently, we are awaiting verification of two more pieces of debris which were discovered recently in Mozambique and Reunion Island respectively," Malaysian Transport Minister Liow Tiong Lai said in a statement.
An interim report will be released by the investigation team on Tuesday marking the two-year anniversary of the disappearance, he said.
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