Malaysia Airlines is the national carrier of Malaysia and one of the largest in Asia
Malaysia Airlines says it has lost contact with a plane travelling from Kuala Lumpur to Beijing, with 239 people on board.
The airline said in a statement that flight MH370 disappeared at 02:40 local time on Saturday (18:40 GMT on Friday).
It was expected to land in Beijing at 06:30 (22:30 GMT).
"Malaysia Airlines is currently working with the authorities who have activated their search and rescue team to locate the aircraft," the carrier said.
"Our team is currently calling the next-of-kin of passengers and crew."
The Boeing B777-200 aircraft was carrying 227 passengers, including two children, and 12 crew members.
"We deeply regret that we have lost all contacts with flight MH370 which departed Kuala Lumpur at 12.41 am earlier this morning bound for Beijing," said the airline.
The flight went missing two hours after taking off from Kuala Lumpur.
China's Xinhua state news agency said it was lost in airspace controlled by Vietnam.
The aircraft did not enter airspace controlled by China and did not make contact with Chinese controllers, the agency added.
Malaysia Airlines has told the BBC it will be holding a press conference later on Saturday.
"Our thoughts and prayers are with all affected passengers and crew and their family members," said its statement.
The airline is the national carrier of Malaysia and one of Asia's largest, flying nearly 37,000 passengers daily to some 80 destinations worldwide.
