British Royal Air Force (RAF) personnel have also been flying in Royal Australian Air Force and Royal New Zealand Air Force maritime patrol aircraft to scour the waters from above, looking for debris and dropping listening buoys, MoD said in a statement.

　　HMS Echo, a British Royal Navy coastal survey ship carrying around 60 search personnel, has scoured an area 6 times the size of Greater London, as the search crews face a race against time before the black box flight recorder stops sending out a signal, according to the ministry.

　　HMS Echo's hi-tech sonar has been specially adapted to pick up any transmissions on the black box's frequency, the first time for the device to be used this way, the MoD added.

　　Although it has located several possible contacts so far, none of them proved to be from MH370's black box.

　　Moreover, HMS Tireless, a Trafalgar Class submarine, is working as part of the coordinated international search, with its sonar listening for the 'ping' signal sent out every second by the black box transponder as long as its battery lasts, the MoD said.

　　So far, the two vessels have not found the black box flight recorder or wreckage from the missing plane.

　　The Royal Australian Navy's vessel Ocean Shield is searching 300 miles to the north, and the British Royal Navy and the Royal Air Force are making a valuable contribution to the Australian-led search for missing Malaysian airliner MH370, according to the MoD.