Perth, Australia: A robotic submarine headed back down into the depths of the Indian Ocean on Friday to scour the seafloor for any trace of the missing Malaysian jet one month after the search began off Australia's west coast, as data from the sub's previous missions turned up no evidence of the plane.
It was the fifth attempt by the Bluefin-21 unmanned sub to find wreckage or the black boxes from Flight 370 in a distant patch of seabed. The sub, which can create sonar maps of the ocean bottom, has now covered 110 square kilometers (42 square miles) of the silt-covered seabed, but has thus far found nothing, the search coordination center said. The sub's last mission hit a record depth beyond its recommended diving parameters, which can potentially cause risk to the equipment, the U.S. Seventh Fleet said in a statement. However, it is being closely monitored.
Officials are desperate to find some physical evidence that they are searching in the right spot for the Boeing 777, which vanished March 8 with 239 on board on a flight from Kuala Lumpur, Malaysia, to Beijing. A weeks-long search of the ocean surface hasn't turned up a single piece of debris, and officials on Thursday determined that an oil slick found in the search zone did not come from the plane.
The Bluefin is searching a remote stretch of ocean floor about 4,500 meters (15,000 feet) deep in an area where sound-locating equipment picked up a series of underwater sounds consistent with an airplane's black box, but it went down to 4,695 meters (15,404 feet) during mission four. Prime Minister Tony Abbott has said officials are "very confident" the sounds came from the Malaysian jet's cockpit voice and flight data recorders, but finding the devices in such deep water is an incredibly difficult task.
Radar and satellite data show the plane flew far off-course and would have run out of fuel in a remote section of the Indian Ocean. Planes and ships have been scouring the ocean surface for a month, to no avail.