Where Is Flight MH370? Robo-Sub Covers Two-Thirds of Search Area

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An unmanned submarine searching for the missing Malaysia Airlines Flight 370 completed two-thirds of its search area without finding any trace of the jet, officials said Monday.

The U.S. Navy-owned Bluefin-21 is scouring a 6-mile radius around the source of a "ping" detected on April 8 that investigators think may have been sent by the plane's black box recorder.

The drone submarine completed its first mission April 13. On Sunday, it completed its eighth mission and a ninth was planned Monday, Australian officials said.

The Bluefin-21 is deployed in the search for missing Malaysia Airlines Flight 370 in the southern Indian Ocean.Lt. Kelli Lunt / AP

As well as the submarine, 10 military aircraft and 11 ships are still engaged in the search more than six weeks after the Boeing 777 went missing on March 8.

The Australian Maritime Safety Authority has planned a visual search area of 19,109 square miles, some 1,081 miles northwest of Perth, Australia.

However, AMSA said Monday this search was threatened by deteriorating weather conditions and Tropical Cyclone Jack, which is heading south toward the northern end of the search area.

Meanwhile, another Malaysia Airlines Boeing 777 bound for Bangalore, India, was forced to turn back and make an emergency landing at Kuala Lumpur after its landing gear malfunctioned on Sunday. The plane's seven crew members and 159 passengers evacuated the aircraft safely.

- Alexander Smith