Story highlights Unprecedented international search resumes

U.S. Navy P-8 Poseidon part of effort

Australian prime minister has "increasing hope" about learning what occurred

Searchers on Saturday did not find floating object

With more planes searching than ever before, Australian Prime Minister Tony Abbott on Sunday expressed optimism the mystery of Malaysia Airlines Flight 370 will be solved.

"We have now had a number of very credible leads, and there is increasing hope -- no more than hope, no more than hope -- that we might be on the road to discovering what did happen to this ill-fated aircraft," Abbott said.

He spoke at a press conference about objects that have been spotted by satellites about 2,400 kilometers (1,500 miles) off Perth.

In one of the great aviation mysteries in history, the airliner carrying 239 people disappeared March 8 after it took off from Kuala Lumpur on a flight to Beijing, CHina.

Malaysian investigators believe it was deliberately diverted by someone on board.

"Obviously, the more aircraft we have, the more ships we have, the more confident we are of recovering whatever material is down there," Abbott said. "And obviously before we can be too specific about what it might be, we do actually need to recover some of this material."

The international search for the missing aircraft resumed early Sunday near Perth, with a U.S. Navy P-8 Poseidon rejoining the effort, according to a naval spokesman.

Eight planes will search over the Indian Ocean on Sunday, compared to six planes on Saturday, said Andrea Hayward-Maher, spokeswoman for the Australian Maritime Safety Authority. She said that would be the most planes yet.

Planes from the United States, New Zealand, Australia and China will be flying. Three planes, two civilian aircraft and the P-8, were airborne by 7 a.m. Perth time (7 p.m. ET).

New Chinese satellite images "will be taken into consideration" in the search, Hayward-Maher said.

The P-8 Posideon, grounded for two days to give its crew rest, will likely refocus on an area highlighted in Chinese satellite images of a large object floating in the area. Australian-led search teams in the southern Indian Ocean found no sign of it Saturday.

The intense air and sea search -- which will now employ NASA satellites -- entered its third week with no new clues to give families answers about the fate of the passengers and crew.

The object the Chinese photographed is 22.5 meters long and 13 meters wide (74 feet by 43 feet), officials said.

China said the satellite images showing the "suspected floating object" were captured on March 18.

As a result of the recently reported satellite sighting approximately 1,500 miles off the coast of Perth, plans are underway to acquire imagery within the next few days, NASA said Saturday.

The space agency said it will check archives of satellite data and use space-based assets such as the Earth-Observing-1 (EO-1) satellite and the ISERV camera on the International Space Station to acquire images of possible crash sites. The resolution of these images could be used to identify objects of about 98 feet (30 meters) or larger.

The Australian Maritime Safety Authority said searchers will take the Chinese information into consideration as they design their search for Sunday.

The floating object was about 77 miles from where earlier satellite images spotted floating debris.

At least six search flights were involved Saturday, including two private jets. Though the two civilian jets did not have radar, their role was crucial, authorities said.

"It is more likely that a pair of eyes are going to identify something floating in the ocean," Australian Deputy Prime Minister Warren Truss said.

Indeed, during Saturday's search it was a civil aircraft that reported sighting some small objects floating with the naked eye, including a wooden pallet, AMSA said. These objects were within a radius of 5 kilometers (3 miles).

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A Royal New Zealand Air Force P-3 Orion was dispatched to the area, but only reported seeing clumps of seaweed, AMSA said.

On Saturday, the Norwegian merchant ship Hoegh St. Petersburg was released from taking part in the search, according to AMSA. Australian officials thanked the ship's crew for its "valuable assistance and efforts," AMSA said via Twitter.

Malaysia Airlines Flight 370 vanished on March 8 with 239 people aboard destined for Beijing from Kuala Lumpur.

The stated goal of the Malaysian authorities is to narrow the search area, a task that is proving difficult.

Intensified, expanded search

The search area expanded sizably on Saturday compared to the previous day, thanks in part to the capabilities of the civil jets.

"Operations continue, and today they plan to search an area of approximately 10,500 square nautical miles," Hishammuddin said Saturday.

In addition to two Chinese planes that arrived in Australia, Beijing is sending two more ships to join five already in the southern corridor.

"Two Indian aircraft, a P-8 Poseidon and a C-130 Hercules, arrived in Malaysia last night to assist with the search," he said.

Seven countries -- China, India, Pakistan, Myanmar, Laos, Kyrgyzstan and Kazakhstan -- informed investigators that based on preliminary information, their nations had no radar sightings of missing jetliner.

Clues, but no proof

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Photos: The search for MH370 Photos: The search for MH370 Two years after Malaysia Airlines Flight 370 went missing, a relative of one of the passengers burns incense in Beijing on March 8, 2016. Flight 370 vanished on March 8, 2014, as it flew from Kuala Lumpur, Malaysia, to Beijing. There were 239 people on board. Hide Caption 1 of 43 Photos: The search for MH370 On July 29, police carry a piece of debris on Reunion Island, a French territory in the Indian Ocean. A week later, authorities confirmed that the debris was from the missing flight. Hide Caption 2 of 43 Photos: The search for MH370 Staff members with the Australian Transport Safety Bureau examine a piece of aircraft debris at their laboratory in Canberra, Australia, on July 20. The flap was found in June by residents on Pemba Island off the coast of Tanzania, and officials had said it was highly likely to have come from Flight 370. Experts at the Australian Transport Safety Bureau, which is heading up the search for the plane, confirmed that the part was indeed from the missing aircraft. Hide Caption 3 of 43 Photos: The search for MH370 In late February, American tourist Blaine Gibson found a piece of plane debris off Mozambique, a discovery that renewed hope of solving the mystery of the missing flight. The piece measured 35 inches by 22 inches. A U.S. official said it was likely the wreckage came from a Boeing 777, which MH370 was. Hide Caption 4 of 43 Photos: The search for MH370 Relatives of the flight's passengers console each other outside the Malaysia Airlines office in Subang, Malaysia, on February 12, 2015. Protesters had demanded that the airline withdraw the statement that all 239 people aboard the plane were dead. Hide Caption 5 of 43 Photos: The search for MH370 A police officer watches a couple cry outside the airline's office building in Beijing after officials refused to meet with them on June 11, 2014. The couple's son was on the plane. Hide Caption 6 of 43 Photos: The search for MH370 Members of the media scramble to speak with Azharuddin Abdul Rahman, director general of Malaysia's Civil Aviation Department, at a hotel in Kuala Lumpur, Malaysia, on May 27, 2014. Data from communications between satellites and the missing flight was released the day before, more than two months after relatives of passengers said they requested it be made public. Hide Caption 7 of 43 Photos: The search for MH370 Operators aboard the Australian ship Ocean Shield move Bluefin-21, the U.S. Navy's autonomous underwater vehicle, into position to search for the jet on April 14, 2014. Hide Caption 8 of 43 Photos: The search for MH370 A member of the Royal New Zealand Air Force looks out of a window while searching for debris off the coast of western Australia on April 13, 2014. Hide Caption 9 of 43 Photos: The search for MH370 The HMS Echo, a vessel with the British Roya; Navy, moves through the waters of the southern Indian Ocean on April 12, 2014. Hide Caption 10 of 43 Photos: The search for MH370 A Royal Australian Air Force AP-3C Orion, on a mission to drop sonar buoys to assist in the search, flies past the Australian vessel Ocean Shield on April 9, 2014. Hide Caption 11 of 43 Photos: The search for MH370 A relative of a missing passenger cries at a vigil in Beijing on April 8, 2014. Hide Caption 12 of 43 Photos: The search for MH370 Australian Defense Force divers scan the water for debris in the southern Indian Ocean on April 7, 2014. Hide Caption 13 of 43 Photos: The search for MH370 A towed pinger locator is readied to be deployed off the deck of the Australian vessel Ocean Shield on April 7, 2014. Hide Caption 14 of 43 Photos: The search for MH370 A member of the Royal New Zealand Air Force looks at a flare in the Indian Ocean during search operations on April 4, 2014. Hide Caption 15 of 43 Photos: The search for MH370 On March 30, 2014, a woman in Kuala Lumpur prepares for an event in honor of those aboard Flight 370. Hide Caption 16 of 43 Photos: The search for MH370 The sole representative for the families of Flight 370 passengers leaves a conference at a Beijing hotel on March 28, 2014, after other relatives left en masse to protest the Malaysian government's response to their questions. Hide Caption 17 of 43 Photos: The search for MH370 A member of the Royal Australian Air Force is silhouetted against the southern Indian Ocean during the search for the missing jet on March 27, 2014. Hide Caption 18 of 43 Photos: The search for MH370 Flight Lt. Jayson Nichols looks at a map aboard a Royal Australian Air Force aircraft during a search on March 27, 2014. Hide Caption 19 of 43 Photos: The search for MH370 People in Kuala Lumpur light candles during a ceremony held for the missing flight's passengers on March 27, 2014. Hide Caption 20 of 43 Photos: The search for MH370 Malaysian Prime Minister Najib Razak, center, delivers a statement about the flight on March 24, 2014. Razak's announcement came after the airline sent a text message to relatives saying it "deeply regrets that we have to assume beyond any reasonable doubt that MH 370 has been lost and that none of those onboard survived." Hide Caption 21 of 43 Photos: The search for MH370 Grieving relatives of missing passengers leave a hotel in Beijing on March 24, 2014. Hide Caption 22 of 43 Photos: The search for MH370 A passenger views a weather map in the departures terminal of Kuala Lumpur International Airport on March 22, 2014. Hide Caption 23 of 43 Photos: The search for MH370 A Chinese satellite captured this image, released on March 22, 2014, of a floating object in the Indian Ocean, according to China's State Administration of Science. It was a possible lead in the search for the missing plane. Surveillance planes were looking for two objects spotted by satellite imagery in remote, treacherous waters more than 1,400 miles from the west coast of Australia. Hide Caption 24 of 43 Photos: The search for MH370 Satellite imagery provided by the Australian Maritime Safety Authority on March 20, 2014, showed debris in the southern Indian Ocean that could have been from Flight 370. The announcement by Australian officials raised hopes of a breakthrough in the frustrating search. Hide Caption 25 of 43 Photos: The search for MH370 Another satellite shot provided by the Australian Maritime Safety Authority shows possible debris from the flight. Hide Caption 26 of 43 Photos: The search for MH370 A distraught relative of a missing passenger breaks down while talking to reporters at Kuala Lumpur International Airport on March 19, 2014. Hide Caption 27 of 43 Photos: The search for MH370 On March 18, 2014, a relative of a missing passenger tells reporters in Beijing about a hunger strike to protest authorities' handling of information about the missing jet. Hide Caption 28 of 43 Photos: The search for MH370 U.S. Navy crew members assist in search-and-rescue operations in the Indian Ocean on March 16, 2014. Hide Caption 29 of 43 Photos: The search for MH370 Members of the Chinese navy continue search operations on March 13, 2014. After starting in the sea between Malaysia and Vietnam, the plane's last confirmed location, search efforts expanded west into the Indian Ocean. Hide Caption 30 of 43 Photos: The search for MH370 A Vietnamese military official looks out an aircraft window during search operations March 13, 2014. Hide Caption 31 of 43 Photos: The search for MH370 Malaysian air force members look for debris near Kuala Lumpur on March 13, 2014. Hide Caption 32 of 43 Photos: The search for MH370 Relatives of missing passengers wait for the latest news at a hotel in Beijing on March 12, 2014. Hide Caption 33 of 43 Photos: The search for MH370 A member of the Vietnamese air force checks a map while searching for the missing plane on March 11, 2014. Hide Caption 34 of 43 Photos: The search for MH370 A Vietnamese air force plane found traces of oil that authorities had suspected to be from the missing Malaysia Airlines plane, the Vietnamese government online newspaper reported on March 8, 2014. However, a sample from the slick showed it was bunker oil, typically used to power large cargo ships, Malaysia's state news agency, Bernama, reported on March 10, 2014. Hide Caption 35 of 43 Photos: The search for MH370 A U.S. Navy Seahawk helicopter lands aboard the USS Pinckney to change crews on March 9, 2014, before returning to search for the missing plane in the Gulf of Thailand. Hide Caption 36 of 43 Photos: The search for MH370 Buddhist monks at Kuala Lumpur International Airport offer a special prayer for the missing passengers on March 9, 2014. Hide Caption 37 of 43 Photos: The search for MH370 Members of a Chinese emergency response team board a rescue vessel at the port of Sanya in China's Hainan province on March 9, 2014. Hide Caption 38 of 43 Photos: The search for MH370 The rescue vessel sets out from Sanya in the South China Sea on March 9, 2014. Hide Caption 39 of 43 Photos: The search for MH370 Malaysian Prime Minister Najib Razak, center, arrives to meet family members of missing passengers at the reception center at Kuala Lumpur International Airport on March 8, 2014. Hide Caption 40 of 43 Photos: The search for MH370 A relative of two missing passengers reacts at their home in Kuala Lumpur on March 8, 2014. Hide Caption 41 of 43 Photos: The search for MH370 Chinese police at the Beijing airport stand beside the arrival board showing delayed Flight 370 in red on March 8, 2014. Hide Caption 42 of 43 Photos: The search for MH370 Malaysia Airlines Group CEO Ahmad Juahari Yahya, front, speaks during a news conference at a hotel in Sepang on March 8, 2014. "We deeply regret that we have lost all contacts" with the jet, he said. Hide Caption 43 of 43

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An exhaustive search covering 2.97 million square miles -- nearly the size of the continental United States -- has yielded some clues, but no proof of where the Boeing 777 is or what happened to it.

One of the most notable leads revolved around two large objects detected by satellite a week ago floating on waters over 1,400 miles off Australia's west coast.

"The fact that it's six days ago that this imagery was captured does mean that clearly what objects were there, are likely to have moved a significant different distance as a result of currents and winds," Truss said.

"It's also possible that they've just drifted to the bottom of the ocean bed, and the ocean in this area is between 3 and 5 kilometers deep. So it's a very, very deep part of the ocean, very remote. And all that makes it particularly difficult."

Debris is a common sight in the waters in that part of the ocean, he said, and includes containers that fall off ships.

Australian Prime Minister Tony Abbott on Friday defended the decision to announce the find, saying Australia owes it to families of those missing "to give them information as soon as it's to hand."

But he didn't make any promises.

"It could just be a container that has fallen off a ship," Abbott said during a visit to Papua New Guinea. "We just don't know."

Malaysia's interim transportation minister tried to reset expectations for a quick resolution to the mystery after the satellite discovery.

"This is going to be a long haul," Hishammuddin Hussein said.

Search intensifies

U.S. Defense Secretary Chuck Hagel ordered the Navy and policy experts to look at the availability and usefulness of U.S. military undersea technology to try to find the plane's wreckage and its data recorders, a U.S. military official said.

The United States has spent $2.5 million so far on the entire effort, Pentagon spokesman Col. Steven Warren said Friday.

First lady Michelle Obama, while on a trip to Beijing, said the United States is keeping the families of the missing passengers in its thoughts.

"As my husband has said, (the) United States (is) offering as many resources as possible to assist in the search," she said.

Global search

Countries from central Asia to Australia are also engaged in the search along an arc drawn by authorities based on satellite pings received from the plane hours after it vanished. One arc tracks the southern Indian Ocean zone that's the focus of current attention.

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Map: The search area

"We intend to continue the search until we are absolutely satisfied that further searching would be futile, and that day is not in sight," the deputy prime minister said. "We will continue the effort, we'll continue to liaise with our international allies in this search."

The other tracks over parts of Cambodia, Laos, China and into Kazakhstan.

Malaysian authorities were awaiting permission from Kazakhstan's government to use the country as a staging area for the northern corridor search, Hishammuddin said.

Malaysia Airlines CEO Ahmad Jauhari Yahya told reporters Saturday that a transcript obtained by The Telegraph newspaper is "inaccurate," but did not provide additional details.

The Telegraph reported Friday it had a transcript documenting 54 minutes of back-and-forth between the cockpit and ground control from taxiing in Kuala Lumpur to the final message of "All right, good night."

Unexplained element

The alleged transcript reported by The Telegraph contains seemingly routine conversations about which runway to use and what altitude to fly at.

One unexplained element, according to the British newspaper, is a call, in which someone in the cockpit stated that the aircraft was at a cruising altitude of 35,000 feet -- something that had been done just six minutes earlier. Twelve minutes after that comes the "good night" message, at around the time Flight 370 was being transferred to Vietnam's control.

Another wrinkle: Malaysia Airlines chief executive officer Ahmad Jauhari Yahya said the plane was carrying a cargo of lithium-ion batteries, although he didn't specify the volume of the shipment.

Lithium-ion batteries are commonly used in laptops and cell phones, and have been known to explode, although that occurs rarely.

They were implicated in the fatal crash of a UPS cargo plane in Dubai in 2010, and lithium-ion batteries used to power components on Boeing 787s were blamed for fires in those planes.

There's no evidence the batteries played a role in the plane's disappearance, and Ahmad said they are routine cargo aboard aircraft.

"They are not declared dangerous goods" he said, adding that they were "some small batteries, not big batteries."

Malaysian authorities say they believe the missing plane was deliberately flown off course on its scheduled flight from Kuala Lumpur to Beijing.