SYDNEY - Australian and American planes drew a blank Wednesday on the first full day of a search across a vast tract of the southern Indian Ocean for missing Malaysia Airlines flight MH370.
Authorities in Kuala Lumpur on Monday asked Canberra to take responsibility for the "southern vector" of the operation to locate the Boeing 777 that disappeared on March 8 en route to Beijing with 239 passengers and crew on board.
The Malaysian government believes the jet was deliberately diverted and flew for several hours after leaving its scheduled flight path - either north towards Central Asia, or towards the southern Indian Ocean.
While one sortie was flown late Tuesday, the search kicked into full gear with three long-range Australian, American and New Zealand surveillance planes involved on Wednesday, scouring an area of 305,000 square kilometres (122,000 sq miles) - bigger than either Italy or the Philippines.
Five merchant ships also responded to a broadcast for shipping to help issued by Australia's Rescue Coordination Centre.
"Three ships have transited through the area, another is in the area today and a further ship is expected to arrive on Thursday afternoon," said the Australian Maritime Safety Authority, which is in charge of the search.
"Neither the ships nor the aircraft have reported sighting anything in connection to the aircraft."
The search Wednesday focused on an area 2,600 kilometres south-west of Perth, based on the last known satellite and military radar data received from the plane, coupled with analysis of possible routes if it had flown south.
Australian officials said on Tuesday it was like looking for a needle in a haystack, and they reiterated the slim chances of finding any surface wreckage with planes not equipped to look underwater.
"This area is vast and remote. It is a challenging search operation and AMSA continues to hold grave fears for the passengers and crew on board the missing flight," AMSA said.