UK & World News
MH370: Mini-Sub Second Wreckage Search Under Way
A mini-submarine tasked with finding wreckage from the missing Malaysia Airlines plane has had its second search mission called off after it developed a technical problem.
The US Navy's Bluefin-21 submarine's first mission was aborted after six hours on Monday because the ocean waters where it was sent were too deep.
What data it did managed to gather has been analysed, and no sign of flight MH370 has been found.
The Boeing 777 vanished en route from Kuala Lumpur to Beijing with 239 people on board more than five weeks ago.
Investigators believe it crashed in the southern Indian Ocean but they do not know why.
The unmanned sub is programmed to hover 30 metres (100ft) above the ocean floor, but during its first descent it began searching a patch that was deeper than its maximum operating depth of 4,500 metres (15,000ft).
A built-in safety feature returned it to the surface and there was no damage to the submarine.
Eleven military planes and three civilian aircraft are searching a 21,000 square mile (55,000 square km) area of ocean centred 1,300 miles (2,000km) northwest of Perth. Eleven ships are also involved.
Isolated showers are forecast in the search area, with sea swells of up to two metres and visibility of three miles (five kilometres).
With no sign yet of any wreckage from the jet despite weeks of searching, authorities have acknowledged that the days of the surface hunt are numbered.
The focus now has moved under the waves.
The submarine is programmed to take 24 hours to finish each mission: two hours to get to the bottom, 16 hours to search the sea floor, two hours to return and then a further four hours to upload the data.
It can create a three-dimensional sonar map of any debris on the ocean floor.
But this could prove challenging because the seabed is covered in silt that could potentially cover wreckage.