Story highlights U.S. Navy sending listening device to help find voice and data recorders if wreckage is found

Source: Plane changed altitude, flying as low as 12,000 feet after making short turn

Schiavo: Altitude information "explains so many pieces that didn't fit together"

10 aircraft set to comb southern region for missing plane as search resumes Monday

As a growing number of airplanes scoured the southern Indian Ocean in the search for Malaysia Airlines Flight 370, authorities released new details that paint a different picture of what may have happened in the plane's cockpit.

Military radar tracking shows that the aircraft changed altitude after making a sharp turn over the South China Sea as it headed toward the Strait of Malacca, a source close to the investigation into the missing flight told CNN. The plane flew as low as 12,000 feet at some point before it disappeared from radar, according to the source.

The sharp turn seemed to be intentional, the source said, because executing it would have taken the Boeing 777 two minutes -- a time period during which the pilot or co-pilot could have sent an emergency signal if there had been a fire or other emergency onboard.

Authorities say the plane didn't send any emergency signals, though some analysts say it's still unclear whether the pilots tried but weren't able to communicate because of a catastrophic failure.

The official, who is not authorized to speak to the media, told CNN that the area the plane flew in after the turn is a heavily trafficked air corridor and that flying at 12,000 feet would have kept the jet well out of the way of that traffic.

Earlier Sunday, Malaysian authorities said the last transmission from the missing aircraft's reporting system showed it heading to Beijing -- a revelation that appears to undercut the theory that someone reprogrammed the plane's flight path before the co-pilot signed off with air-traffic controllers for the last time.

That reduces, but doesn't rule out, suspicions about foul play in the cockpit.

The new details give more insight about what happened on the plane, but don't explain why the plane went missing or where it could be.

Analysts are divided about what the latest information could mean. Some argue it's a sign that mechanical failure sent the plane suddenly off course. Others say there are still too many unknowns to eliminate any possibilities.

CNN aviation analyst Miles O'Brien called the fresh details about the flight a "game changer."

"Now we have no evidence the crew did anything wrong," he said. "And in fact, now, we should be operating with the primary assumption being that something bad happened to that plane shortly after they said good night."

A satellite image released by China shows an object in the southern Indian Ocean.

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If a crisis on board caused the plane to lose pressure, he said, pilots could have chosen to deliberately fly lower to save passengers onboard.

"You want to get down to 10,000 feet, because that is when you don't have to worry about pressurization. You have enough air in the atmosphere naturally to keep everybody alive," he said. "So part of the procedure for a rapid decompression ... it's called a high dive, and you go as quickly as you can down that to that altitude."

Military radar tracked the flight between 1:19 a.m. and 2:40 a.m. the day it went missing, the source told CNN, but it's not clear how long it took the plane to descend to 12,000 feet.

The new details about altitude are "highly significant," said Mary Schiavo, a CNN aviation analyst and former inspector general for the U.S. Department of Transportation.

"It explains so many pieces that didn't fit together before," she said. "Now, if we have a scenario where something happened, the plane made a dramatic turn and dropped from 35,000 feet to 12,000 feet, this scenario would fit what a pilot would do in the event of a catastrophic onboard event, such as a rapid decompression, a fire, an explosion. That's what you would have to do, descend, get down and turn around and try to get back to an airport that could accommodate an ailing plane."

If the latest information is accurate, the theory of pilots trying to save the plane fits, said Mark Weiss, a former American Airlines pilot and CNN aviation analyst.

But that's a big if, he said.

"We've had so much information come out and so much contradictory information come out, that I caution against jumping to any types of conclusions at this point," he said.

Challenging search

As speculation over what led to the flight's disappearance showed no signs of slowing, investigators appeared to be beefing up their efforts to comb the southern Indian Ocean.

Buoyed by a third set of satellite data that indicated possible debris from the plane in the water, the international team led by Australia fought bad weather as it looked for signs of the Boeing 777 and the 239 people who were aboard when the plane went missing on March 8.

The search for the missing Malaysia Airlines plane resumed Monday morning, with additional aircraft joining the operation, Australian authorities said. The Australian Maritime Safety Authority said 10 aircraft will search for possible objects in an area about 2,500 kilometers (1,550 miles) southwest of Perth.

That includes two jets from China and two from Japan, which were on the way to join the search area on Monday, authorities said.

France's Foreign Ministry said Sunday that radar data from a satellite pointed to floating debris in the Indian Ocean 2,300 kilometers (1,430 miles) from Perth, Australia. The data were immediately passed along to Malaysian authorities, and French satellite resources will home in more on the area, the ministry said.

Satellite images previously issued by Australian and Chinese authorities have also captured possible large floating objects, stoking hopes searchers may find debris from the missing plane.

But so far, searchers have turned up empty-handed after more than two weeks of scouring land and sea.

On Saturday, searchers found a wooden pallet as well as strapping belts, the Australian Maritime Safety Authority's John Young said. The use of wooden pallets is common in the airline industry.

"It's a possible lead ... but pallets are used in the shipping industry as well," he said Sunday. Authorities have said random debris is often found in the ocean.

The flying distance to and from the search area presents a big challenge for search aircraft.

"They're operating at the limits of their endurance," said Mike Barton, the authority's rescue coordination chief.

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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If search crews do turn up anything, they'll soon have more technology to help them.

The U.S. Navy is sending a super-sensitive hydrophone listening device to Australia to be on standby if debris from Malaysia Airlines Flight 370 is found and a search for the plane's voice and data recorders can be done, a U.S. military official said Sunday. The device is pulled behind a ship at slow speeds and is used by the Navy to locate downed aircraft to a depth of 20,000 feet.

Was turn reprogrammed?

Malaysian officials, in a written update Sunday on the search, cast doubt on the theory that someone, perhaps a pilot, had reprogrammed the aircraft to make an unexpected left turn during the flight.

"The last ACARS transmission, sent at 1:07 a.m., showed nothing unusual. The 1:07 a.m. transmission showed a normal routing all the way to Beijing," it read.

The Aircraft Communications Addressing and Reporting System measures thousands of data points and sends the information via satellite to the airline, the engine manufacturer and other authorized parties, according to CNN aviation and airline correspondent Richard Quest.

Had the plane been reprogrammed to change course, the ACARS system should have reported it during its last communication at 1:07. The ACARS is supposed to report new information every 30 minutes, but it was silent at 1:37.

"It is important because it is more consistent (with an emergency). In other words, if the pilots had put in this waypoint that they were going to turn to and that they knew in advance of their last communication that they were going to turn, then everyone was (saying) that this had to be a premeditated act," Schiavo said. "Now if this information is correct, and it was not premeditated, then it does fit very closely with the scenario that, whatever happened, happened suddenly and they turned perhaps to go back to an emergency airport."

Hope, only hope

Australian Prime Minister Tony Abbott voiced hope that investigators could be closing in on an answer to questions that have dogged authorities for days: What happened to the plane, and where is it?

"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 at a news conference.

In one of the great aviation mysteries in history, the airliner carrying 239 people disappeared March 8 after it took off from Kuala Lumpur, Malaysia, on a flight to Beijing. An exhaustive search covering 2.97 million square miles -- nearly the size of the continental United States -- has yielded some clues but no evidence of where the Boeing 777 is or what happened to it.

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