In Kuala Lumpur, where the plane took off for Beijing, the country's defense minister thanked more than two dozen countries involved in the search that is stretching from Kazakhstan in Central Asia to the southern Indian Ocean, and said the focus remains on finding the airplane.
"This going to be a long haul," Hishammuddin Hussein told a news conference.
The search area indicated by the satellite images — some 2,500 kilometers (1,550 miles) southwest of Perth — is so remote it takes aircraft four hours to fly there and four hours back, leaving them with only enough fuel to search for about two hours.
On Friday, five planes, including three P-3 Orions, made the trip. While search conditions had improved from Thursday, with much better visibility, the Australian Maritime Safety Authority said there were no sightings of plane debris.
Searchers relied mostly on trained spotters aboard the planes scanning the ocean rather than radar because the use of radar found nothing during the first day of the search on Thursday, Australian officials said.
Going forward, the search will focus more on visual sightings because civilian aircraft are being brought in to participate. The military planes will continue to use both radar and spotters.
"Noting that we got no radar detections yesterday, we have replanned the search to be visual. So aircraft flying relatively low, very highly skilled and trained observers looking out of the aircraft windows and looking to see objects," said John Young, manager of the maritime safety authority's emergency response division.
Two Chinese aircraft are expected to arrive in Perth on Saturday to join the search, and two Japanese aircraft will be arriving Sunday, Truss said. A small flotilla of ships coming to Australia from China was 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," said Truss, who is acting prime minister while Tony Abbott is in Papua New Guinea.
Experts say it is impossible to tell if the grainy satellite images of the two objects — one 24 meters (almost 80 feet) long and the other measuring 5 meters (15 feet) — were debris from the plane. But officials have called this the best lead so far in the search that began March 8 after the plane vanished over the Gulf of Thailand on an overnight flight to Beijing.
For relatives of the people aboard the plane — 154 of the 227 passengers are Chinese — hope was slipping away, said Nan Jinyan, sister-in-law of passenger Yan Ling.
"I'm psychologically prepared for the worst and I know the chances of them coming back alive are extremely small," said Nan, one of dozens of relatives gathered at a Beijing hotel awaiting any word about their loved ones.
Abbott spoke with Chinese President Xi Jinping, whom he described as "devastated."
"It's about the most inaccessible spot that you could imagine on the face of the Earth, but if there is anything down there we will find it. We owe it to the families of those people to do no less," Abbott said.