Surveillance teams from the United States have been sent to the Indian Ocean as the search for missing Malaysian Airlines flight MH370 continues to widen.
The move follows claims the plane may have flown for longer after its last communication than investigators initially thought.
The Boeing 777-200ER disappeared on Saturday with 239 people on board.
The plane was on route from Kuala Lumpur to Beijing and last made contact with air-traffic control over the South China Sea to the east of Malaysia.
Latest reports suggest the aircraft could have returned signals to satellites for up to five hours after the last voice communication with air traffic control.
However, this has not been confirmed by officials in Malaysia.
The US has now sent a navy destroyer and a sophisticated surveillance aircraft to the Indian Ocean, hundreds of miles west of Malaysia.
India, another of a number of countries helping in the search for the plane, has deployed its navy, air force and coast guard after a request for help from the Malaysian government.
Over half of the people on board the aircraft were Chinese, and Beijing has been putting pressure on Malaysia to intensify its search.