Senior Colonel Do Duc Minh (R), deputy chief of staff of the Vietnam Air Force, leaves an AN-26 after performing flight safety checks, before the aircraft departs for a mission to find the missing Malaysia Airlines flight MH370, at a military airport in Ho Chi Minh city March 11, 2014. The so-far fruitless search for a missing Malaysian airliner entered its fourth day on Tuesday, as sources in Europe, the United States and Asia voiced growing scepticism that the flight lost with 239 people on board was the target of an attack. The massive search has drawn in navies, military aircraft, coastguard and civilian vessels from 10 nations, but failed to turn up any trace of the Boeing 777-200ER that vanished about an hour into a flight from Kuala Lumpur to Beijing early on Saturday. REUTERS/Kham (VIETNAM - Tags: DISASTER TRANSPORT MILITARY)