The planes are part of an international effort to solve the nearly 2-week-old mystery of what happened to Flight 370 with 239 people aboard. They are looking for two large floating objects detected by a satellite off the southwest coast of Australia, about halfway to the desolate islands of the Antarctic.
"The last report I have is that nothing of particular significance has been identified in the search today, but the work will continue," said Warren Truss, who is acting prime minister while Tony Abbott is in Papua, New Guinea.
Truss told reporters that two Chinese aircraft are expected to arrive in Perth on Saturday to join the search, and two Japanese aircraft will be arriving on Sunday. A small flotilla of ships coming to Australia from China is still several days away.
"We are doing all that we can, devoting all the resources we can and we will not give up until all of the options have been exhausted," Truss said. "We can't be certain that the sightings are in fact debris from the aircraft (but) it is about the only lead that is around at the present time."
The search area in the southern Indian Ocean is so remote is takes aircraft four hours to fly there and four hours back, leaving them only about two hours to search.
The satellite discovery raised new hopes of finding the jet and sent another emotional jolt to the families of the people on board.
John Young, manager of the Australian Maritime Safety Authority's emergency response division, said five planes were sent out Friday.
Young said the weather improved from Thursday, but there was still some low cloud cover over the search area, 2,300 kilometers (1,400 miles) from western Australia.
The aircraft are planning to head back to the search zone on Saturday, but the search area will change slightly depending on water movements overnight, Young said.
The anguished relatives of the passengers have been highly critical of Malaysian officials for delays in releasing information.
In Beijing, relatives met Friday with Malaysian officials at a hotel where most have been staying awaiting news. Attendees said they had a two-hour briefing about the search but that nothing new was said.
The hunt has encountered other false leads. Oil slicks that were seen did not contain jet fuel. A yellow object thought to be from the plane turned out to be sea trash. Chinese satellite images showed possible debris, but nothing was found.
Malaysian authorities have not ruled out any possible explanation for what happened to the jet, but have said the evidence so far suggests it was deliberately turned back across Malaysia to the Strait of Malacca, with its communications systems disabled. They are unsure what happened next.
Police are considering the possibility of hijacking, sabotage, terrorism or issues related to the mental health of the pilots or anyone else on board.
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Gelineau reported from Sydney, Australia. Associated Press writers Rod McGuirk and Todd Pitman in Kuala Lumpur; Nick Perry in Wellington, New Zealand; and Christopher Bodeen in Beijing contributed to this report.
