The search for missing Malaysia Airlines Flight MH370 could take years, U.S. Navy officials suggested on Sunday, as search and rescue officials raced to locate the plane's black box recorder days before its batteries are set to die.
Ten ships and as many aircraft are searching a massive area in the Indian Ocean west of Perth, trying to find some trace of the aircraft, which went missing more than three weeks ago and is presumed to have crashed.
The chief of the China Maritime Search and Rescue Center, He Jianzhong, told the Xinhua state news agency no objects linked to the plane had been found on Sunday, and that Chinese vessels would expand their search area.
Numerous objects have been spotted in the two days since Australian authorities moved the search 1,100 km (685 miles) after new analysis of radar and satellite data concluded the Boeing 777 travelled faster and for a shorter distance after vanishing from civilian radar screens on March 8. None has been confirmed as coming from Flight MH370.
U.S. Navy Captain Mark Matthews, who is in charge of the U.S. Towed Pinger Locator (TPL), told journalists at Stirling Naval Base near Perth that the lack of information about where the plane went down seriously hampers the ability to find it.
"Right now the search area is basically the size of the Indian Ocean, which would take an untenable amount of time to search," he said.
"If you compare this to Air France flight 447, we had much better positional information of where that aircraft went into the water," he said, referring to a plane that crashed in 2009 near Brazil and which took more than two years to find.
The U.S. Navy cannot use the pinger locator and other sonar used to listen for the beacons on the aircraft's flight data and cockpit voice recorders until "conclusive visual evidence" of debris is found, U.S. Navy spokesman Commander William Marks told CBS' "Face the Nation" programme.
If no location is found, searchers would have to use sonar to slowly and methodically map the bottom of the ocean, he said. "That is an incredibly long process to go through. It is possible, but it could take quite a while," he said.
Among the vessels to join the search is an Australian defence force ship, the Ocean Shield, that has been fitted with a sophisticated U.S. black box locator and an underwater drone.
Australia, which is coordinating the search