The search area for the missing Malaysian jet has proved too deep for a robotic submarine which was hauled back to the surface of the Indian Ocean less than halfway through its first seabed hunt for wreckage and the all-important black boxes, AP quoted authorities as saying on Tuesday. Search crews sent the U.S. Navy's Bluefin 21 deep into the Indian Ocean on Monday to begin scouring the seabed for the missing Malaysia Airlines Boeing 777 after failing for six days to detect any signals believed to be from its black boxes. But just six hours into its planned 16-hour mission on the sea bed, the unmanned sub exceeded its maximum depth limit of 4,500 meters (15,000 feet) and its built-in safety feature returned it to the surface, the search coordination center said in a statement. The data collected by the Bluefin on Monday was analyzed after it returned to the surface and nothing of interest was found, the U.S. Navy said in a statement.
