Urgent search for jet's black boxes
The search for the missing Malaysia Airlines jet has entered a new stage as navy ships deployed stingray-shaped sound locators in a remote stretch of the Indian Ocean, in an increasingly urgent hunt for the plane's data recorders before their beacons fall silent.
Officials leading the multinational search for Flight 370 said there was no specific information that led to the underwater devices being used for the first time, but that they were brought into the effort because there was nothing to lose.
An arduous weeks-long hunt has not turned up a single piece of wreckage that could have led the searchers to the plane and eventually to its black boxes, which contain key information about the flight.
Beacons in the black boxes emit "pings" so they can be more easily found. The beacons' batteries last about a month.
Commander Peter Leahy, who is leading the military forces involved in the search, said: "No hard evidence has been found to date, so we have made the decision to search a sub-surface area on which the analysis has predicted MH370 is likely to have flown."
Two ships with sophisticated equipment that can hear the pings made their way along a 150 mile (240km) route investigators hope may be close to the spot Flight 370 entered the water after it vanished on March 8 on a flight from Kuala Lumpur, Malaysia, to Beijing, China.
The head of the joint agency co-ordinating the search acknowledged that the search area was essentially just a best guess - and noted time is running out to find the coveted data recorders.
Angus Houston said: "The locater beacon will last about a month before it ceases its transmissions - so we're now getting pretty close to the time when it might expire."
The Australian navy ship Ocean Shield towed a pinger locator from the US Navy and the British navy's HMS Echo, equipped with similar gear, looked for the black boxes in an area investigators' settled on after analysing hourly satellite pings the aircraft gave off after it disappeared.
That information, combined with data on the estimated speed and performance of the aircraft, led them to that specific stretch of ocean, Mr Houston said.
Because the US Navy's pinger locator can pick up black box signals to a depth of 20,000ft (6,100m), it should be able to hear the plane's data recorders even if they are lying in the deepest part of the search zone - about 19,000ft (5,800m) below the surface.
But that's only if the locator gets within range of the black boxes - a tough task, given the size of the search area and the fact that the pinger locator must be dragged slowly through the water at just one to five knots, or one to six miles per hour.
The type of locator being used is a 30in (70cm)-long, cylindrical microphone that is towed underwater in a grid pattern behind a ship.
It is attached to about 20,000ft (6,100m) of cable and is guided through the ocean depths by a yellow, triangular carrier with a shark fin on top. It looks like a stingray and has a wingspan of 3ft (a metre).
Finding floating wreckage is key to narrowing the search area, as officials can then use data on ocean currents to try and backtrack to the spot where the Boeing 777 hit the water - and where the black boxes may be. The devices would provide crucial information about what condition the plane was flying under and any communications or sounds in the cockpit.
But with no wreckage found so far, officials cannot be confident they are looking for the black boxes in the right place, said Geoff Dell, discipline leader of accident investigation at Central Queensland University in Australia.
"They might be lucky and they might start smack bang right over the top of it," Mr Dell said. "But my guess is that's not going to be the case and they're in for a lengthy search."
The area where crews are looking for the devices lies within a larger 84,000 square mile (217,000 square kilometre) search zone that 14 planes and nine ships criss-crossed in the hopes of spotting debris on the ocean surface. The search zone is about 1,100 miles (1,700km) north-west of the Australian west coast city of Perth.
Fourteen aircraft and 11 ships were involved in today's search activities in the greater search areas, the co-ordination agency said. Ships sighted a number of objects in the area but none were associated with the missing plane.
The search area has shifted each day, as the investigative team continues to analyse what little radar and satellite data is available while factoring in where any debris may have drifted due to ocean currents and weather.
Australia is co-ordinating the ocean search, and the investigation into the plane's disappearance is ultimately Malaysia's responsibility. Australia, the US, Britain and China have all agreed to be "accredited representatives" of the investigation.
Four Australian investigators were in Malaysia to help with the investigation and ensure information on the aircraft's likely flight path is fed back to search crews.
The two countries are still working out who will be in charge of analysing any wreckage and flight recorders that may be found.