Search crews sent a robotic submarine deep into the Indian Ocean for the first time Monday after failing to pick up any signals from the missing Malaysian airliner's black boxes for six days. Crews have picked up a series of underwater sounds over the past two weeks that are consistent with signals from an aircraft's black boxes, which contain flight data and cockpit voice recordings. The devices emit "pings" so they can be more easily found, but their batteries last only about a month, and it has been more than a month since the plane vanished.
Bluefin-21 remotely controlled unmanned submarine
Spotlight search technique will take as long as a day
Searchers say this will be a slow, painstaking process
Graphics source: BBC and Graphic News
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