Search and rescue teams are trying to find a Malaysia Airlines plane that has gone missing with more than 200 passengers on board.
The airline lost contact with the B777-200 aircraft after it departed Kuala Lumpur shortly after 12.40am local time on Saturday.
It was expected to land in Beijing at 6.30am.
Flight MH370 was carrying 227 passengers including two infants and 12 crew members.
Malaysia Airlines said in a statement that it was working with the authorities who have activated their search and rescue team to locate the aircraft.
An unconfirmed report from a flight tracking website said the plane had plunged more than 200 metres and changed course in the last minute that it had transmitted data.
The airline will provide regular updates on the situation.
Australian authorities are trying to confirm whether there were any Australian passengers on board the missing flight, a spokeswoman for the Department of Foreign Affairs and Trade said.
Chinese authorities have reportedly said the flight never entered Chinese airspace.
A flight-tracking website said communication was lost 20 minutes after departure from Kuala Lumpur.
"It doesn't sound very good," retired American Airlines captain Jim Tilmon told CNN on Saturday.
He said that the route was mostly overland, which meant that there would be plenty of radars and radios to contact the plane.
"I've been trying to come up with every scenario that I could just to explain this away, but I haven't been very successful."
He said the plane was "about as sophisticated as any commercial airplane could possibly be".
Some websites listed the plane as having landed at 6.10am in Beijing but Malaysian Airlines issued the statement to report it was missing at 7.54am.
The missing plane is believed to have been involved in a crash in August, 2012, when it damaged the tail of a China Eastern Airlines plane at Shanghai Pudong Airport, according to unconfirmed reports.
In the incident, the tip of the wing of the Malaysia Airlines Boeing 777 broke off.
Malaysia Airlines has just released a statement saying its "thoughts and prayers" were with all the passengers on board the missing plane, and their families.
Passengers of 13 nationalities were on board the plane.
"[The] focus of the airline is to work with the emergency responders and authorities and mobilize its full support," chief executive Ahmad Jauhari Yahya said.
"Our team is micurrently calling the next-of-kin of passengers and crew."
Malaysia Airlines is the national carrier of Malaysia and one of Asia's largest, flying nearly 37,000 passengers daily to some 80 destinations worldwide.
The airline said the public can call +60-378841234 for information about the plane.
Licenced pilot John Preston said that rumours that the aircraft has made an emergency landing in Nanming are unlikely.
"I think we can safely discount that."
He said Chinese authorities had confirmed the plane had not entered their airspace. He said there were several ways for the aircraft to communicate with the authorities but that does not appear to have happened.
More to come