It has been revealed a yellow floating object found in the South China Sea off Vietnam is not a life raft.
It had been thought it could belong to the missing Malaysia Airlines plane.
There has been no sign of the Boeing 777 since Friday night and hijacking remains a key line of inquiry.
Todd Curtis, a former safety engineer at Boeing, says a beacon that can transmit the plane's location would not function if it was underwater, but there is another way the aircraft can give investigators its whereabouts.