Australian Prime Minister Tony Abbott is warning that the search for the missing Malaysia Airlines flight is likely to be long after pings believed to be from locator beacons on the all-important black boxes fell silent, meaning the batteries have most probably died.
The last of four strong signals coming from 4,500 meters (15,000 feet) below the surface were heard on the 8 April. The batteries on the black boxes, which record flight data including conversations from the cockpit, only last a month, meaning the window has passed.
The pings already captured have however allowed the search area to be narrowed down to a 500-square-mile patch of the seabed - about the size of Los Angeles. Once officials are confident no more sounds will be heard, and the search area can be narrowed no further, a robotic submersible will be sent down to slowly scour for wreckage across the vast area.
The Bluefin 21 submersible will take six times longer to cover the same area as the ping locator, and will need about six weeks to two months to canvass the current underwater zone.