MH370: Underwater drone Bluefin-21 aborted mission, returns early

The autonomous underwater vehicle Bluefin-21 - said to be the search's best hope for finding Malaysia Airlines Flight 370 - has aborted it's first mission and returned to the surface of the Indian Ocean.

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The mission was supposed to take 24 hours to map the first portion of the search area: 16 hours to map, four hours' of travel time to the ocean floor and back, and four hours to analyze the data gathered.

In an interview with CNN's Erin Burnett, Captain Mark Matthews, who heads the U.S. presence in the search effort, explains why the underwater robot returned to the surface earlier than planned.