US submarine embarks on second-day mission to hunt for MH370

A robotic submarine searching for the missing MH370 jet has begun its second mission after cutting short its first after facing hurdles.

The first 16-hour search by the US Navy's Bluefin 21 submarine lasted just six and none of the data collected offered clues to the whereabouts of the plane.

According to news24, the unmanned sub is programmed to hover 30m above the seabed, but it started search was deeper than the sub's maximum operating depth of 4 500m, the search coordination centre and the US Navy said.

A built-in safety feature returned the Bluefin to the surface and it was not damaged, they said.

The US Navy said that the crew has now shifted the search zone away from the deepest water before sending the Bluefin back for Tuesday's mission.

According to the report, the submarine is programmed to take 24 hours to complete each mission: two hours to dive to the bottom, 16 hours to search the seafloor, two hours to return to the surface, and four hours to upload the data.