Cookie consent

We use cookies to improve your experience on this website. By continuing to browse our site you agree to our use of cookies. Tell me more | Cookie preferences

More pings raise more questions about missing plane

What you need to know about a black box

    Just Watched

    What you need to know about a black box

What you need to know about a black box 01:51

Story highlights

  • U.S. Navy commander: Initial optimism over pulse signals becomes more cautious
  • Search officials call new pulse signals the best indication so far they are on the right track
  • Without wreckage from the missing plane, nothing is certain for now
  • Finding an answer will take time, officials warn

Almost a month after Malaysia Airlines Flight 370 disappeared, searchers say pulse signals detected in the Indian Ocean provide the best hope so far for finding it.

However, those same officials warn it will take time to confirm if the sonar pings come from the missing plane, meaning nothing is certain yet.

The new information raises more questions about what the pulse signals mean and what happens now.

Is this it?

Maybe.

An Australian ship using high-tech U.S. equipment has twice detected signals along the suspected flight path of the airliner off its country's western coast.

U.S. search official: 'It won't be quick'

    Just Watched

    U.S. search official: 'It won't be quick'

U.S. search official: 'It won't be quick' 03:31
PLAY VIDEO
Searching for Underwater Sounds

    Just Watched

    Searching for Underwater Sounds

Searching for Underwater Sounds 05:04
PLAY VIDEO
U.S. pinger locator detects two signals

    Just Watched

    U.S. pinger locator detects two signals

U.S. pinger locator detects two signals 01:10
PLAY VIDEO

Angus Houston, who heads the rescue effort, told reporters that a device called a towed pinger locator on the vessel Ocean Shield received signals similar to the kind that the aircraft's on board data and cockpit voice recorders would emit.

The first detection, which occurred over the weekend, lasted more than two hours before the ship lost contact, Houston said. A second detection several hours later lasted 13 minutes, and more importantly, included two separate signals audible to the locator device, he said.

Two signals could mean they came from the so-called black boxes, as expected.

"It's probably the best information that we have had," Houston said before immediately noting that "we haven't found the aircraft yet; we need further confirmation."

A promising lead

Why this may be it

The signals reported were near the 37.5 kHz "standard beacon frequency" of the recorders, officials say. That frequency was chosen for use to avoid interference from other ocean noises as much as possible.

In addition, the two pulse signals detected at the same time would be consistent with the two emitters on the plane.

Also, the location where the signals were detected is along the missing plane's probable flight path, according to the latest analysis of its known direction and fuel capacity. Houston said the new information on the likely flight path helped narrow the search area.

"With the acoustic events that we're getting in the area, we are encouraged that we're very close to where we need to be," Houston said, later adding: "This is quite an extraordinary set of circumstances that we're now in a very well-defined search area which hopefully will eventually yield the information that we need to say MH370 might have entered the water just here."

On Saturday, a Chinese ship detected a single pulse signal more than 300 miles further south, also near the most recently projected flight path. Houston said the distance made it "unlikely" the Chinese ship and Australian vessel detected the same signal, but added "in deep water, funny things happen with acoustic signals."

Why this may not be it

From the beginning, search officials have stressed the long odds against figuring out where the plane might be without visible evidence such as wreckage.

For now, all we have are some pulse signals, Houston said, and in the ocean, those could be from a number of things.

"This has been done without finding any wreckage thus far, and I think it's quite extraordinary and what I'd like to see now is us find some wreckage because that will basically help solve the mystery," Houston explained, adding that "without wreckage, we can't say it's definitely here."

Next steps

Oceanographers note that the ocean is full of sonar sounds, including whale calls and signals emitted by research equipment left on the bottom to help find it later. While the frequency of the black box signals are intended to be unique, other sounds can cause confusion, they note.

"Unlike in air where sound travels in a straight line, acoustic energy -- sound through the water -- is greatly affected by temperature, pressure and salinity," explained Peter Leavy, commander of the military task force conducting the search. "And that has the effect of attenuating, bending -- sometimes through 90 degrees -- sound waves. So it is quite possible and very hard to predict -- it's quite possible for sound to travel great distances laterally but be very difficult to hear near the surface of the ocean, for instance."

On Monday, U.S. Navy Commander William Marks told CNN from the search operation that the inability of the Ocean Shield's pinger locator to find the signals again more than a day since the last reception caused initial optimism to become "more and more cautious."

What next?

The Ocean Shield and its towed pinger locator continue to search the area where it detected the signals to try to hear them again. If they do, searchers would send out a Bluefin-21 Autonomous Underwater Vehicle with a more accurate sonar and possibly a camera for mapping and studying the the ocean floor, Leavy said.

"At the moment that's not deployed," he told reporters. "The focus is on trying to reacquire the acoustic signal that they had" by the end of Tuesday.

Meanwhile, the website MarineTraffic.com indicated Monday that three ships were searching a spot further to the south where the Haixun 01, a Chinese patrol boat, reportedly detected pulse signals on Saturday.

Another Chinese vessel and the HMS Echo of Britain's Royal Navy joined the Haixun 01 in the area, according to the website, which has been reliable in reporting the movements of search vessels.

Officials had said they would send additional resources to help the Haixun 01 try to find the source of pulse signals it detected on the same 37.5 kHz frequency used by airplane recorders.

A major question is how long the batteries in the recorders will last. They have a 30-day expectancy when activated, and the plane disappeared on March 8, which was 31 days ago.

"We're already one day past the advertised shelf life," Houston said. "We hope that it keeps going for a little bit longer."

Relatives react

Confirmation that the signal comes from the Boeing 777 would mean "the possibility of recovering the plane -- or at least the black boxes -- goes from being one in a million to almost certain," said Simon Boxall, a lecturer in ocean and earth science at the University of Southampton.

Houston, a retired Australian Air chief marshal who is chief coordinator of Joint Agency Coordination Centre, warned against expecting a quick resolution.

"It could take some days before the information is available to establish whether these detections can be confirmed as being from MH370," he said. "In very deep oceanic water, nothing happens fast."

What happens after the pingers die?

      Malaysia Airlines Flight 370

    • nr intv moni basu husbands quiet suffering flight 370_00020822.jpg

      His wife never came home from her flight on MH370, and now K.S. Narendran is left to imagine the worst of possible truths without knowing.
    • This handout photo taken on April 7, 2014 and released on April 9, 2014 by Australian Defence shows Maritime Warfare Officer, Sub Lieutenant Ryan Penrose watching HMAS Success as HMAS Perth approaches for a replenishment at sea while searching for missing Malaysia Airlines flight MH370 in the southern Indian Ocean. Two fresh signals have been picked up Australian ship Ocean Shield in the search for missing Malaysian flight MH370, raising hopes that wreckage will be found within days even as black box batteries start to expire.

      Was the sound of Malaysian Airlines Flight MH370 striking the water captured by ocean devices used to listen for signs of nuclear blasts?
    •  A crew member of a Royal New Zealand Airforce (RNZAF) P-3K2-Orion aircraft helps to look for objects during the search for missing Malaysia Airlines flight MH370 in flight over the Indian Ocean on April 13, 2014 off the coast of Perth, Australia. S

      What was believed to be the best hope of finding the missing plane is now being called a false hope. Rene Marsh explains.
    • Caption:A Chinese relative of passengers on the missing Malaysia Airlines flight MH370 uses a lighter as she prays at the Metro Park Hotel in Beijing on April 8, 2014. The hunt for physical evidence that the Malaysia Airlines jet crashed in the Indian Ocean more than three weeks ago has turned up nothing, despite a massive operation involving seven countries and repeated sightings of suspected debris. AFP PHOTO/WANG ZHAO (Photo credit should read WANG ZHAO/AFP/Getty Images)

      Involved parties, including the manufacturer Boeing, are bracing for a long public relations siege.
    • The painstaking search for Malaysia Airlines Flight 370 got a vote of confidence Friday that the effort is headed in the right direction, but officials noted that much work remains.
Credit: 	CNN

      Official: The four acoustic pings at the center of the search for Flight 370 are no longer believed to have come from the plane's black boxes.
    • INDIAN OCEAN (April 14, 2014) -- Operators aboard ADF Ocean Shield move U.S. Navy's Bluefin-21 into position for deployment, April 14. Using side scan sonar, the Bluefin will descend to a depth of between 4,000 and 4,500 meters, approximately 35 meters above the ocean floor. It will spend up to 16 hours at this depth collecting data, before potentially moving to other likely search areas. Joint Task Force 658 is currently supporting Operation Southern Indian Ocean, searching for the missing Malaysia Airlines Flight 370. (U.S. Navy video by Mass Communication Specialist 1st Class Peter D. Blair/RELEASED)

      The underwater search for the missing Malaysia Airlines plane will effectively be put on hold this week, and may not resume until August at the earliest.
    • Movie-makers say they have recruited leading Hollywood technicians to bring their experience to mid-air flight sequences.

      Movie-makers in Cannes have announced they're making a thriller based on the disappearance of Malaysian flight MH370.
    • The search for the missing Boeing 777 has gone on for eight weeks now. CNN's David Molko looks back at this difficult, emotional assignment.