Lost jet: Most difficult search in history for MH370 continues

The search for the missing Malaysia Airlines flight MH370 ended for the day Thursday with no sightings made in the search area in the southern Indian Ocean yet again and Australian Prime Minister Tony Abbott said the search operation is "the most difficult in human history".

"At the end of the day, 10 aircraft and nine ships were involved in search activities," Australia's Joint Agency Coordination Centre (JACC) said in its latest update.

"Three aircraft searched in the southern search area of 248,000 square kilometres, 1,700 km west north west of Perth," it said.

"There have been no sightings of any objects reported today."

Stating that the weather in the search area was fair, with visibility approximately 10 km, the JACC said the search area was being continually adjusted and Thursday it moved north.

"The Royal Navy hydrographic ship HMS Echo also operated in the northern area searching for sonic transmissions from the flight data recorder. One alert was experienced but discounted. False alerts may be experienced from biological sources such as whales or interference from shipping noise," it added.

Malaysia Airlines flight MH370 vanished mysteriously about an hour after taking off from Kuala Lumpur shortly after midnight March 8.

The Boeing 777-200ER was scheduled to land in Beijing the same day. The 227 passengers on board included five Indians, 154 Chinese and 38 Malaysians.

Earlier Thursday, Australian Prime Minister Tony Abbott said the ongoing search for missing Malaysia Airlines flight MH370 is "the most difficult in human history", while reiterating his promise to the families of those on board that his country will continue the current search process as best as they can.

In a joint press conference with his visiting Malaysian counterpart Najib Razak, Abbott told reporters this was probably the most difficult search ever undertaken, but "as far as Australia is concerned, we are throwing everything we have" to search for the aircraft, Xinhua reported.

"This is a very tough time for Prime Minister Najib... the search area is moving north, but it's still a remote and inaccessible area... it's the most difficult in human history," said the Australian leader.

He also asked the families of those on board the lost jet to be "patient", saying Australia and the multinational forces will not let them down and would provide the warmest possible welcome if they wanted to come to Australia.

On his part, Malaysian Prime Minister Razak thanked the efforts by Australia and other countries involved in the search operation, saying "their commitment will not be forgotten".

"In a time of great tragedy... differences have been set aside, as 26 nations have united behind a common cause. The disappearance of MH370 is without precedent, so too is the search," said the Malaysian prime minister.

"The disappearance of MH370 has tested our collective resolve. Faced with so little evidence, and such a difficult task, investigators from Australia, China, France, Malaysia, the UK and the US have worked without pause to reveal the aircraft's movements. Their collective efforts have led us here," he added.

Razak also asserted that his country would not give up, because he knew "many families cannot start to grieve until the plane is found".

According to the JAAC update, the two prime ministers also spoke to personnel at the Royal Australian Air Force (RAAF) Base Pearce near Perth, the hub of the aerial search, where they honoured the efforts of the eight nations involved.

"It was a very heart-warming experience to be introduced to the leaders of the various countries -- from China, from the United States, from New Zealand, from Japan, from South Korea, from New Zealand and, of course, from both Australia and Malaysia," Prime Minister Razak said.

"I know it is a daunting task to go out there in very inclement weather, in very challenging circumstances. Malaysia is indeed grateful for your courage and for your commitment."

Razak also announced that Australia had accepted Malaysia's invitation to participate as an accredited representative in the investigation and would continue to work closely together to draw up a comprehensive agreement on the search.