File photo of a Malaysian Airlines Boeing 777, similar to the jet that is missing over the South China Sea, presumed crashed, on Saturday.
A Malaysia Airlines jet has gone missing over Southeast Asia with 239 people aboard.
Vietnam authorities said contact with Flight MH370 was lost near its airspace, but its exact location and what happened to it remained a mystery 12 hours after it slipped off air-traffic control screens.
Malaysia Airlines said the plane, on an overnight flight from Kuala Lumpur to Beijing, relayed no distress signal, indications of rough weather, or other signs of trouble.
Meanwhile the search is continuing as relatives wait anxiously.
Malaysia Airlines has long been a respected name in regional aviation, enjoying an enviable safety record.
The incident will be a major blow to the airline, which has struggled to remain profitable recently against a host of nimble competitors, particularly the rise of budget airlines.
The plane that disappeared Saturday somewhere over the South China Sea -- believed near Vietnam airspace -- was a Boeing 777-200, considered one of the safest planes in the industry.
The model is the oldest in the Boeing 777 family and has a range of 5,240 nautical miles (9,700 kilometres), according to the Boeing website. Its typical cruising speed at 35,000 feet is Mach 0.84.
Boeing 777 family of long-range, wide body, twin-engined planes have a solid safety record and have been among the world's most widely-flown passenger jets since first entering service in 1995.(Mar 8, 2014 10:00 PM ET // by AFP)