The Boeing 777 was en-route from Kuala Lumpur to Beijing when contact was lost.
239 people aboard. If confirmed lost, it will be the worst air disaster involving a Boeing 777.
The first commercial flight of the 777 was on 7 June 1995 and is Boeing's first 'Fly By Wire' commercial aircraft.
http://www.bbc.co.uk/news/world-asia-26492748