Kuala Lumpur, Malaysia (CNN) — After a month of searching, investigators now have their “most promising” lead yet in finding the missing plane.
A pinger locator in the Indian Ocean has detected signals consistent with those emitted by aircraft black boxes, the head of the Joint Agency Coordination Center said Monday.
The sounds were heard at a depth of 4,500 meters (about 14,764 feet), retired Air Chief Marshal Angus Houston said.
But it could take days before officials can confirm whether the signals did indeed come from the plane, which went missing March 8 with 239 people on board, the search official said.
“Nothing happens fast,” Houston said. He said the latest clues merit further investigation.
Along with the hints that searchers may be getting close to the plane, a fresh mystery surfaced Sunday.
The aircraft skirted Indonesian airspace as it went off the grid and veered off course, a senior Malaysian government source told CNN.
The new analysis of the flight’s path means the plane may have been taken along a route designed to avoid radar detection, the source said.
But why would someone steer the plane that way, and where is it now?
Source: MH370 skirted Indonesia radar
Source: MH370 skirted Indonesia radar
Official: Search teams detect 2nd pulse
Those are key questions that investigators are trying to answer — and fast.
The HMS Echo, a British navy ship equipped with advanced detection gear, sailed into the area of the southern Indian Ocean on Monday morning (Sunday afternoon ET) where a Chinese crew had detected two audio signals.
And an Australian navy vessel carrying sophisticated U.S. listening technology is investigating a sound it picked up in a different patch of the ocean.
Investigators hope the signals could be locator beacons from the plane’s data recorders, but they’re not sure yet.
Time could be running out. It might be only a few hours or a few days before the pingers aboard the plane stop transmitting for good.
The batteries inside the beacons, which are designed to start sending signals when a plane crashes into water, last about 30 days after the devices are activated.
That 30th day has come — though experts have said it’s possible that they could last several days longer if they were at their full strength.
Plane said to have flown around Indonesia
As searchers tried to find the aircraft, investigators pieced together new details about the plane’s path.
After reviewing radar track data from neighboring countries, officials have concluded that the passenger jet curved north of Indonesia before turning south toward the southern Indian Ocean, a senior Malaysian government source told CNN on Sunday.
Whoever was flying the plane, the source said, could have been trying to avoid radar detection.
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Like most details in the case that’s baffled investigators ever since the plane dropped off Malaysian military radar, it depends on whom you ask.
CNN law enforcement analyst Tom Fuentes cautioned against assuming a nefarious reason for steering the plane around Indonesia’s airspace.
“I think the plane’s being intentionally flown there, but I think it’s still a mystery as to why. … I think they would probably guess they’re not avoiding anybody’s radar, because there’s a lot of radar in the area,” he said. “I think they’re avoiding getting shot down or colliding with another airplane.”
CNN aviation analyst Miles O’Brien said the new route includes designated waypoints that pilots and air traffic controllers use.
“This particular route that is laid out happens to coincide with some of these named intersections,” he said. “So what it shows is an experienced pilot somewhere in the mix on this.”
Investigators haven’t yet said who they think might have flown the plane off course or why.
The possibility that the plane was hijacked by someone who knew how to fly a commercial jet is still on the table. Authorities have also been investigating the plane’s captain and co-pilot. And they haven’t ruled out mechanical problems as a possible cause of the plane’s diversion.
So far, no physical evidence of the plane’s eventual whereabouts has been found, leaving many relatives of those on board trapped in uncertainty.
Time is running out
The arrival of the Echo will be critical to the search for the missing Boeing 777. It has state-of-the-art sonar and is capable of mapping the ocean floor, which is about 4,500 meters (2.8 miles) deep in the focused search area.
It should be able to help determine more confidently whether audio signals picked up on Friday and Saturday by the Chinese patrol ship Haixun 01 have any connection to the pingers from MH370.
But officials urged caution. In the lengthy search for the missing plane, promising discoveries nearly every day have fizzled out, with few facts to support them.
“This is an important and encouraging lead, but one that I urge you to continue to treat carefully,” Angus Houston, the head of the Australian agency coordinating search operations, said Sunday.
The Chinese said the electronic pulses — detected only 2 kilometers (1.25 miles) apart — were consistent with those emitted by pingers on an aircraft’s black boxes, but search officials said they haven’t been verified as coming from Flight 370.
A member of the Royal New Zealand Air Force looks at a flare in the Indian Ocean on Friday, April 4, during search operations for Malaysia Airlines Flight 370. Authorities are combing thousands of square miles of the southern Indian Ocean in search of Flight 370, which disappeared March 8.
Members of the Royal New Zealand Air Force monitor data April 4 on board an aircraft during search operations.
A relative of a Flight 370 passenger watches television in a Beijing hotel as he awaits new information about the missing plane on Thursday, April 3.
Another relative of a Flight 370 passenger waits for updates in Beijing on Wednesday, April 2. Many families have criticized the Malaysian government’s handling of information in the plane’s disappearance.
A member of the Japanese coast guard points to a flight position data screen while searching for debris from the missing jet on Tuesday, April 1.
Kojiro Tanaka, head of the Japanese coast guard search mission, explains the efforts en route to the search zone April 1.
A woman prepares for an event in honor of those aboard Flight 370 on Sunday, March 30, in Kuala Lumpur, Malaysia.
An underwater search-surveying vehicle sits on the wharf in Perth, Australia, ready to be fitted to a ship to aid in the search for the jet.
A girl in Kuala Lumpur writes a note during a ceremony for the missing passengers on March 30.
A teary-eyed woman listens from the back as other relatives of Flight 370 passengers speak to reporters March 30 in Subang Jaya, Malaysia. Dozens of anguished Chinese relatives demanded that Malaysia provide answers to the fate of those on board.
An object floating in the southern Indian Ocean is seen from a Royal New Zealand Air Force P-3K2 Orion aircraft searching for the missing jet on Saturday, March 29. Ships participating in the search retrieved new debris Saturday, but no objects linked to the missing plane, according to Australian authorities.
A Royal New Zealand Air Force member launches a GPS marker buoy over the southern Indian Ocean on March 29.
The sole representative for the families of Flight 370 passengers leaves a conference at a Beijing hotel on Friday, March 28, after other relatives left en masse to protest the Malaysian government’s response to their questions.
A member of the Royal Australian Air Force is silhouetted against the southern Indian Ocean during the search for the missing jet on Thursday, March 27.
Flight Lt. Jayson Nichols looks at a map aboard a Royal Australian Air Force aircraft during a search on March 27.
People in Kuala Lumpur light candles during a ceremony held for the missing flight’s passengers on March 27.
Crew members of the Chinese icebreaking ship Xuelong scan the Indian Ocean during a search for the missing jet on Wednesday, March 26.
People work at a console at the British satellite company Inmarsat on Tuesday, March 25, in London.
The mother of a passenger who was on Malaysia Airlines Flight 370 cries at her home in Medan, Indonesia, on March 25.
Australian Defense Minister David Johnston speaks to the media March 25 about the search for the missing jet.
A family member of a missing passenger reacts after hearing the latest news March 25 in Kuala Lumpur.
Angry relatives of those aboard Malaysia Airlines Flight 370 react in Beijing on Monday, March 24, after hearing that the plane went down over the southern Indian Ocean, according to analysis of satellite data.
Grieving relatives of missing passengers leave a hotel in Beijing on March 24.
Malaysian Prime Minister Najib Razak, center, delivers a statement about the flight March 24 in Kuala Lumpur. 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.”
Relatives of the missing passengers hold a candlelight vigil in Beijing on March 24.
A member of the Royal Australian Air Force looks out an aircraft during a search for the missing jet March 24.
A woman reads messages for missing passengers at a shopping mall in Kuala Lumpur on March 24.
Flight Lt. Josh Williams of the Royal Australian Air Force operates the controls of an AP-3C Orion on Sunday, March 23, after searching the southern Indian Ocean.
Ground crew members wave to a Japanese Maritime Defense Force patrol plane as it leaves the Royal Malaysian Air Force base in Subang, Malaysia, on Sunday, March 23. The plane was heading to Australia to join a search-and-rescue operation.
A passenger views a weather map in the departures terminal of Kuala Lumpur International Airport on Saturday, March 22.
A Chinese satellite captured this image, released on March 22, of a floating object in the Indian Ocean, according to China’s State Administration of Science. It is a possible lead in the search for the missing plane. Surveillance planes are looking for two objects spotted by satellite imagery in remote, treacherous waters more than 1,400 miles from the west coast of Australia.
A member of the Royal Australian Air Force looks down at the Norwegian merchant ship Hoegh St. Petersburg, which took part in search operations Friday, March 21.
The Royal Australian Air Force’s Neville Dawson, left, goes over the search area with Brittany Sharpe aboard an AP-3C Orion some 2,500 kilometers (about 1,500 miles) southwest of Perth, Australia, over the Indian Ocean on March 21.
Satellite imagery provided by the Australian Maritime Safety Authority on Thursday, March 20, shows debris in the southern Indian Ocean that could be from Flight 370. The announcement by Australian officials that they had spotted something raised hopes of a breakthrough in the frustrating search.
A closer look at the satellite shot of possible debris from Malaysia Airlines Flight 370.
Another satellite shot provided by the Australian Maritime Safety Authority shows possible debris from the flight.
A closer look at the satellite shot of possible debris.
The Australian Maritime Safety Authority’s John Young speaks to the media in Canberra, Australia, on March 20 about satellite imagery.
A distraught relative of a missing passenger breaks down while talking to reporters at Kuala Lumpur International Airport on Wednesday, March 19.
A relative of missing passengers waits for a news briefing by officials in Beijing on Tuesday, March 18.
A relative of a missing passenger tells reporters in Beijing about a hunger strike to protest authorities’ handling of information about the missing jet.
A member of Indonesia’s National Search and Rescue Agency joins in a search for the missing plane in the Andaman
Sea area around the northern tip of Indonesia’s Sumatra on Monday, March 17.
Relatives of missing passengers watch a news program about the missing plane as they await information at a hotel ballroom in Beijing on March 17.
Malaysian Transportation Minister Hishamuddin Hussein, center, shows maps of the search area at a hotel next to the Kuala Lumpur International Airport on March 17.
U.S. Navy crew members assist in search-and-rescue operations Sunday, March 16, in the Indian Ocean.
Indonesian personnel watch over high seas during a search operation in the Andaman Sea on Saturday, March 15.
A foam plane, which has personalized messages for the missing flight’s passengers, is seen at a viewing gallery March 15 at Kuala Lumpur International Airport.
A member of the Malaysian navy makes a call as his ship approaches a Chinese coast guard ship in the South China Sea on March 15.
A Indonesian ship heads to the Andaman Sea during a search operation near the tip of Sumatra, Indonesia, on March 15.
Elementary school students pray for the missing passengers during class in Medan, Indonesia, on March 15.
Col. Vu Duc Long of the Vietnam air force fields reporters’ questions at an air base in Ho Chi Minh City, Vietnam, after a search operation on Friday, March 14.
Members of the Chinese navy continue search operations on Thursday, March 13. The search area for Flight 370 has grown wider. After starting in the sea between Malaysia and Vietnam, the plane’s last confirmed location, efforts are expanding west into the Indian Ocean.
A Vietnamese military official looks out an aircraft window during search operations March 13.
Malaysian air force members look for debris on March 13 near Kuala Lumpur.
A relative of a missing passenger watches TV at a Beijing hotel as she waits for the latest news March 13.
A member of the Indonesian National Search and Rescue Agency scans the horizon in the Strait of Malacca on Wednesday, March 12.
Relatives of missing passengers wait for the latest news at a hotel in Beijing on March 12.
Journalists raise their hands to ask questions during a news conference in Sepang on March 12.
Indonesian air force officers in Medan, Indonesia, examine a map of the Strait of Malacca on March 12.
A member of the Vietnamese air force checks a map while searching for the missing plane on Tuesday, March 11.
Iranians Pouri Nourmohammadi, second left, and Delavar Seyed Mohammad Reza, far right, were identified by Interpol as the two men who used stolen passports to board the flight. But there’s no evidence to suggest either was connected to any terrorist organizations, according to Malaysian investigators. Malaysian police believe Nourmohammadi was trying to emigrate to Germany using the stolen Austrian passport.
An Indonesian navy crew member scans an area of the South China Sea bordering Indonesia, Malaysia and Thailand on Monday, March 10.
Vietnam air force Col. Le Huu Hanh is reflected on the navigation control panel of a plane that is part of the search operation over the South China Sea on March 10.
Relatives of the missing flight’s passengers wait in a Beijing hotel room on March 10.
A U.S. Navy Seahawk helicopter lands aboard the USS Pinckney to change crews before returning to search for the missing plane Sunday, March 9, in the Gulf of Thailand.
Members of the Fo Guang Shan rescue team offer a special prayer March 9 at Kuala Lumpur International Airport.
A handout picture provided by the Malaysian Maritime Enforcement Agency shows personnel checking a radar screen during search-and-rescue operations March 9.
Italian tourist Luigi Maraldi, who reported his passport stolen in August, shows his current passport during a news conference at a police station in Phuket island, Thailand, on March 9. Two passengers on the missing Malaysia Airlines flight were reportedly traveling on stolen passports belonging to Maraldi and an Austrian citizen whose papers were stolen two years ago.
Hugh Dunleavy, commercial director of Malaysia Airlines, speaks to journalists March 9 at a Beijing hotel where relatives and friends of the missing flight’s passengers are staying.
Vietnamese air force crew stand in front of a plane at Tan Son Nhat airport in Ho Chi Minh City on March 9 before heading out to the area between Vietnam and Malaysia where the airliner vanished.
Buddhist monks at Kuala Lumpur International Airport offer a special prayer for the missing passengers on March 9.
The Chinese navy warship Jinggangshan prepares to leave Zhanjiang Port early on March 9 to assist in search-and-rescue operations for the missing Malaysia Airlines flight. The Jinggangshan, an amphibious landing ship, is loaded with lifesaving equipment, underwater detection devices and supplies of oil, water and food.
Members of a Chinese emergency response team board a rescue vessel at the port of Sanya in China’s Hainan province on March 9. The vessel is carrying 12 divers and will rendezvous with another rescue vessel on its way to the area where contact was lost with Malaysia Airlines Flight 370.
The rescue vessel sets out from Sanya in the South China Sea.
A family member of missing passengers is mobbed by journalists at Kuala Lumpur International Airport on Saturday, March 8.
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 March 8. 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.
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.
Malaysia Airlines official Joshua Law Kok Hwa, center, speaks to reporters in Beijing on March 8.
A relative of two missing passengers reacts at their home in Kuala Lumpur on March 8.
Wang Yue, director of marketing of Malaysia Airlines in China, reads a company statement during a news conference at the Metro Park Lido Hotel in Beijing on March 8.
Chinese police at the Beijing airport stand beside the arrival board showing delayed Flight 370 in red on March 8.
A woman asks a staff member at the Beijing airport for more information on the missing flight.
A Malaysian man who says he has relatives on board the missing plane talks to journalists at the Beijing airport on March 8.
Passengers walk past a Malaysia Airlines sign on March 8 at Kuala Lumpur International Airport.
Malaysia Airlines Group CEO Ahmad Juahari Yahya, front, speaks during a news conference on March 8 at a hotel in Sepang. “We deeply regret that we have lost all contacts” with the jet, he said.
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Sounds travel long distances underwater, Houston said, making it difficult to ascertain their sources. If detectors were near a pinger, they would pick up the signal for a more sustained period.
Houston also said that search authorities were informed Sunday that the Ocean Shield, an Australian naval vessel equipped with sophisticated listening equipment, has detected “an acoustic noise” in another area of the ocean to the north.
The signals are the latest leads in a huge, multinational hunt for Flight 370, which disappeared almost a month ago over Southeast Asia.
‘Most promising lead’
The Ocean Shield, which has a high-tech pinger locator borrowed from the U.S. Navy, will continue to pursue the sound it heard. If that lead turns cold, it will move to the other detection area, a journey that will take at least a day, officials said.
On Monday morning, the Ocean Shield was “continuing investigations in its own area,” Australian authorities said.
“At the moment, the most promising lead appears to be the one associated with Haixun 01,” Houston said at a news conference in Perth, the Western Australian city serving as a hub for search operations.
The pulses registered by the Chinese ship are of particular interest because they occurred in an area that fits with the latest calculation by experts of roughly where the plane is likely to have entered the water, Houston said.
The area of detection is roughly 1,600 kilometers (1,000 miles) west-northwest of Perth, according to coordinates reported by Chinese state media.
Several analysts on CNN said the information from search officials gave cause for optimism.
“We’ve got to be a little careful about groupthink here, but right now the evidence seems to point towards the Chinese vessel’s location,” said Alan Diehl, a former accident investigator for the U.S. Air Force.
What’s more, white objects were spotted floating on the surface of the water about 90 kilometers (55 miles) from where the sounds were detected, authorities said.
But Houston warned that the latest discoveries could turn out to have no connection to the missing plane.
“In the days, weeks and possibly months ahead, there may be leads such as the one I’m reporting to you this morning on a regular basis,” Houston said.
“I assure that we will follow up and exhaust every credible lead that we receive,” he said.
The Chinese vessel detected the second signal for a total of 90 seconds on Saturday, according to authorities.
“It’s not a continuous transmission,” Houston said. “If you get close to the device, we should be receiving it for a longer period of time.”
A former longtime Navy oceanographer said the Chinese equipment shown on TV didn’t appear to be very sophisticated. Van Gurley told CNN that the gear was designed to be held by human divers and only had short-range capabilities.
“The fact that they’re deploying it right over the side near the ocean surface, they’re getting hits a mile apart, kind of doesn’t add up — but it does require investigation,” said Gurley, now a senior manager at a consulting firm that uses complex mathematical methods to solve problems like finding a missing plane.
Australian authorities are still working on understanding the technology used regarding the data generated by the Haixun 01 as it searches for the missing plane, a source with the Australian Defense Force told CNN.
CNN’s Catherine E. Shoichet and Steve Almasy reported and wrote from Atlanta, and journalist Ivy Sam reported from Kuala Lumpur. Jethro Mullen, Ralph Ellis and Ben Brumfield contributed to this report.