Canberra:
Australia may use more powerful sonar equipment that can delve deeper beneath the Indian Ocean in the hunt for the missing Malaysia Airlines jet as the prime minister said on Wednesday that failure to find any clue in the most likely crash site would not spell the end of the search.
The search coordination center said Wednesday a robotic submarine, the U.S. Navy's Bluefin 21, had so far covered more than 80 percent of the 310-square-kilometer (120-square-mile) seabed search zone off the Australian west coast, creating a three-dimensional sonar map of the ocean floor. Nothing of interest had been found.
The 4.5-kilometer (2.8-mile) deep search area is a circle 20 kilometers (12 miles) wide around an area where sonar equipment picked up a signal on April 8 consistent with a plane's black boxes. But the batteries powering those signals are now dead.
Defense Minister David Johnston said Australia was consulting with Malaysia, China and the United States on the next phase of the search for the plane that went missing March 8, which is likely to be announced next week.
Johnston said more powerful towed side-scan commercial sonar equipment would probably be deployed, similar to the remote-controlled subs that found RMS Titanic 3,800 meters (12,500 feet) under the Atlantic Ocean in 1985 and the Australian WWII wreck HMAS Sydney in the Indian Ocean off the Australian coast, north of the current search area, in 2008.
"The next phase, I think, is that we step up with potentially a more powerful, more capable side-scan sonar to do deeper water," Johnston told The Associated Press.
While the Bluefin had less than one-fifth of the seabed search area to complete, Johnston estimated that task would take another two weeks.
"We want to be very thorough," he said.
Prime Minister Tony Abbott said the airliner's probable impact zone was a swath of sea floor 700 kilometers (430 miles) long and 80 kilometers (50 miles) wide.
He said a new search strategy would be adopted if nothing was found in the current seabed search zone.
"If at the end of that period we find nothing, we are not going to abandon the search, we may well rethink the search, but we will not rest until we have done everything we can to solve this mystery," Abbott told reporters.
"We owe it to the families of the 239 people on board, we owe it to the hundreds of millions - indeed billions - of people who travel by air to try to get to the bottom of this. The only way we can get to the bottom of this is to keep searching the probable impact zone until we find something or until we have searched it as thoroughly as human ingenuity allows at this time," he said.
The Bluefin's first 16-hour sea floor mission last week was aborted because the water depth exceeded its 4.5 kilometer safety limit. Johnston said it was possible that wreckage had been missed in that deep water.
The focus of next phase of the seafloor search and whether it will include the initial search area would be decided on by continuing analysis of information including flight data and sound detections of suspected beacons, he said.
"We are currently gathering all of the facts together to mount a further assault on the most likely location, given all the facts," he said. "But can I say, it is one hell of a vast area."
"A lot of this seabed has not even been hydrographically surveyed before - some of it has - but we're flying blind," he said, adding that the seabed in the vicinity of the search was up to 7 kilometers (4 miles) deep.
"The whole thing is extraordinarily complex in one of other most isolated parts of the ocean on the planet in very deep water," he added.
The air search for debris would likely continue until a new search phase was announced next week, he said.
The search center said up to 10 planes and 12 ships would join Wednesday's search of an expanse covering 38,000 square kilometers (14,500 square miles), centered 1,600 kilometers (1,000 miles) northwest of the city of Perth.
Radar and satellite data show the jet carrying 239 passengers and crew veered far off course on March 8 for unknown reasons during a flight from Kuala Lumpur, Malaysia, to Beijing. Analysis indicates it would have run out of fuel in the remote section of ocean where the search has been focused. Not one piece of debris has been recovered since the massive multinational hunt began.