SYDNEY (AFP) - Everything "humanly possible" was being done to find the missing Malaysia Airlines MH370, Australian Prime Minister Tony Abbott has vowed.

Mr Abbott, who first announced the potential breakthrough to parliament on Thursday, again cautioned that they were looking in "a remarkably isolated location in very deep and inaccessible ocean".

"Nevertheless, we are throwing all the resources we can at it," he said late Thursday after arriving in Papua New Guinea for a visit.

"We will do everything we humanly can to try to get to the bottom of this.

"We don't know what that satellite saw until we can get a much better, much closer, look at it. But this is the first tangible breakthrough in what up until now has been an utterly baffling mystery."

Grainy satellite imagery taken on Sunday detected a pair of floating objects in the southern Indian Ocean. Malaysia and Australia called the images a "credible" lead in the drawn-out hunt for the jet that vanished on March 8 with 239 passengers and crew on board.

But four planes from Australia, New Zealand and the United States that flew over a 23,000-square kilometre area of ocean some 2,500 kilometres southwest of Perth on Thursday saw nothing of significance, with the search hampered by low cloud.

But conditions are improving, Australia's Bureau of Meteorology told AFP.

"Showers associated with the passage of a cold front on Thursday, which saw low cloud and drizzle affect visibility, are easing," the bureau said.

New Zealand Air Commodore Mike Yardley, commenting to TV3 on the sortie flown by the New Zealand P3 Orion on Thursday, warned that "there's a lot of debris out there in the ocean".

"Our crews picked up debris out there that was not part of the aircraft," he said.

"Our radar will pick up containers that have fallen off container vessels as well, and last night our radar system was picking up marine life - whales and dolphins."