The search for the Malaysia Airlines plane deep in the Indian Ocean was cut short again today when technical problems forced a US Navy underwater drone to surface without finding anything.
A massive air and sea search for missing Malaysian Airlines flight MH370 is continuing almost 1,200 miles off the coast of Perth.
Hope has been pinned on the Bluefin-21 autonomous underwater vehicle finding the first concrete sign of the plane in more than six weeks of hunting.
Malaysian authorities have still not ruled out mechanical problems as causing the Boeing 777's disappearance.
However, they say evidence suggests it was deliberately diverted from its scheduled route from Kuala Lumpur to Beijing.
An aircraft's black box records data from the cockpit and conversations among flight crew and may provide answers about what happened to the missing plane.
An unspecified technical problem meant the Bluefin resurfaced early today and analysis of the sonar data downloaded showed no significant detections.
It was subsequently relaunched to continue its search.
The drone was forced to end its first deployment early on Monday after it exceeded its 4.5km (14,750 feet) depth limit in the remote stretch of ocean.
Search authorities believe the plane crashed there after its disappearance on 8 March with 239 people on board.
The introduction of the Bluefin marks a methodical, slower paced new phase of the search, which is now in its 40th day.
The search has been described by the search coordinator, retired Air Chief Marshal Angus Houston, as the most expensive in aviation history.
US Naval personnel have said the drone could take up to two months to scour a 600sq.km area where the plane is believed to have gone down.
The deep sea area now being searched, the Zenith Plateau, has never been mapped in detail because it is not in any country's economic zone.