PERTH, Australia — Frustration grew Saturday over the lack of progress tracking down two objects spotted by satellite that might be Malaysia Airlines Flight 370, with a Malaysian official expressing worry that the search area will have to be widened if no trace of the plane is found.
Nothing has been found in the three days that search crews have been scouring the area where the satellite took images of objects, about 2,500 kilometers (1,550 miles) southwest of Australia. Two military planes from China arrived in Perth to join Australian, New Zealand and U.S. aircraft in the search. Japanese planes will arrive Sunday and ships were in the area or on their way.
Australian Prime Minister Tony Abbott, on an official visit to Papua New Guinea, said weather hampered the search earlier but conditions were improving.
"There are aircraft and vessels from other nations that are joining this particular search because tenuous though it inevitably is, this is nevertheless the first credible evidence of anything that has happened to Flight MH370," Abbott said.
In Kuala Lumpur, Malaysian Defense Minister Hishammuddin Hussein told reporters that if the search is unsuccessful, the focus will have to return to two broad arcs where pings from the aircraft, detected by another satellite, may have originated. Though direct contact with the aircraft was lost early March 8 over the Gulf of Thailand, the pings continued for several hours after that. One arc stretches into central Asia; the other deep in the Indian Ocean.
"My biggest concern is that if we are not able to identify the debris, having to go back to the two corridors is a huge and massive area," Hishammuddin said.
The Boeing 777 disappeared March 8 with 239 people on board less than an hour after taking off from Kuala Lumpur. Hopes that the search could be more narrowly focused grew after a satellite spotted two large objects in the area earlier this week.
One of the objects was 24 meters (almost 80 feet) in length and the other was 5 meters (15 feet). The objects could be unrelated to the plane; one possibility is that they fell off one of the cargo vessels that travel in the area.
Warren Truss, Australia's acting prime minister while Abbott is abroad, said a complete search could take a long time.
"It is a very remote area, but we intend to continue the search until we're absolutely satisfied that further searching would be futile — and that day is not in sight," he said.
"If there's something there to be found, I'm confident that this search effort will locate it," Truss said from the base near Perth that is serving as a staging area for search aircraft.
Aircraft involved in the search include two ultra-long-range commercial jets and four P3 Orions, the Australian Maritime Safety Authority said.
Because the search area is a four-hour flight from land, the Orions can search for about only two hours before they must fly back. The commercial jets can stay for five hours before heading back to the base.
Two merchant ships were in the area, and the HMAS Success, a navy supply ship, was due to arrive late Saturday afternoon.
Australian maritime officials also were checking for updated satellite imagery. The satellite images that show the objects were taken March 16, but the search in the area did not start until Thursday because it took time to analyze them.
The Chinese planes that arrived in Perth on Saturday were expected to begin searching on Sunday. A small flotilla of ships from China will also join the hunt, along with a refueling vessel that will allow ships to stay in the search area for a long time, Truss said.
The missing plane, which had been bound for Beijing, carried 154 Chinese. In the Chinese capital on Saturday, relatives of the passengers rose up in anger at the end of a brief meeting with Malaysia Airlines and Malaysian government officials.
"You can't leave here! We want to know what the reality is!" they shouted in frustration over what they saw as officials' refusal to answer questions. The relatives gave reporters a statement saying they believe they have been "strung along, kept in the dark and lied to by the Malaysian government."
Malaysia asked the U.S. for undersea surveillance equipment to help in the search, said Rear Adm. John Kirby, a Pentagon spokesman. Defense Secretary Chuck Hagel promised to assess the availability of the technology and its usefulness in the search, Kirby said. The Pentagon says it has spent $2.5 million to operate ships and aircraft in the search and has budgeted another $1.5 million for the efforts.
The Telegraph newspaper in London carried a report showing a transcript of the conversation between the pilots and traffic control before the plane disappeared. The paper said it may have been noteworthy because one of the pilots repeated his altitude about the same time a transponder was turned off.
But Peter Marosszeky, an aviation expert at the University of New South Wales in Australia, said he did not think the transcript was unusual and cautioned against reading too much into it.
Some questions had been raised about the cargo of the missing plane because it contained lithium ion batteries. Malaysia Airlines issued a statement saying it was in compliance with the International Civil Aviation Organization and the International Air Transport Association requirements and classified as "non-dangerous goods."
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 possibilities of hijacking, sabotage, terrorism or issues related to the mental health of the pilots or anyone else on board.