Transcript for Search Crews Race to Find Flight 370 Before Pinging Stops
This is a special room. Under the sea the search for that missing plane Malaysians like trees having nearly four weeks later. Still no pain detective from those black boxes has two ships are towing underwater devices in hopes of picking up a Trace any sign any new clue. In the search and when I'm down Cutler -- New York the ships have so much space to cover ABC's Karen -- joining us now from Washington with the latest on those efforts Karen. Good afternoon Dan no pains but even more importantly no wreckage so at this point this search crews are going to an area of very large area as you said. But they're not sure if there even in the right spot at this point there really just making -- gas. The clock is ticking in the search for Malaysia airlines flight 37. The batteries on the black boxes are only supposed to last for thirty detainees. And that's Sunday priced on the continuing -- -- Information. The search area was adjusted to commit the area a little -- the north. Two ships are dragging sophisticated pain -- caters along a 150 mile route. And the deep waters of the Indian Ocean. The black boxes give off paying that can be detected by the sophisticated equipment on the ships searchers are hoping -- get there in time before -- -- -- Four weeks after the plane disappeared not a single piece of wreckage has been found. In the absence of any debris here's the key the searchers don't really know where to tone of these high tech listening devices. So there taking -- best -- tonight by denying. He strand transport safety bureau. Continues to refine the area. -- crop might have entered the water and a. Finding the wreckage after the data recorder stopped giving -- -- is possible but it will be very difficult. Even -- time was running out there is still hope today in Malaysia. -- -- -- -- Dan the black box batteries will run out of full -- sometime this weekend but it could still give off a weak signal but in order for those low caters to pick it up. They may have to be almost directly above it and given that search area that is a very big challenge and. And that was -- one of things when asked you about just how strong these detection devices actually are. The US -- detector could pick up something that is about 20000. Feet -- so that means even the deepest parts of the Indian Ocean this search area and it is very deep water the deepest part is about 191000. Feet deep so it could take it out. But you know we keep talking about that needle in the haystack they really are talking about that they're gonna have to be right about that the clock is ticking. To have that full strains because that weak signal would be much harder to pick up. And Dan we're not talking about a very speedy process here these ships are moving at the most about six miles per. Our right ABC's carriage -- and Washington on the latest on the search for that Karen thank you appreciate it I want to bring -- ABC news aviation consultant and former NTSB investigator Tom -- It -- as we just heard from Karen there are dragging he's paying locating devices beneath the service of the Indian Ocean. Are -- looking for needle in the haystack or they simply just looking for the haystack itself at this point. What they -- a right -- bracing looking for -- haystack itself. I liken it to being a darkened ballroom looking for a marble -- keep going back and forth back and forth to you find it. It's very difficult but this station have no other choice. The -- -- run out of the day or two maybe even a week if -- the batteries are very good. And where else we have to do we have no wreckage yet to start the search. What then are the chances then of because it is such a wide area -- -- two devices that are being. Pulled along this very expansive. Search field. What are the chances and they're gonna -- the pick up these elusive -- that from these two boxes. Well I I think the odds are very low. But the odds are much lower -- don't try at all. And so they're give -- their best shot they've done a lot of analysis as to bust period a look. -- all what you do now is get people out there and we might get lucky certainly. The last four weeks we have had a -- to work on we have nothing to lose the stage. One of these payers is attached to the flight data recorder the other is to the cockpit voice recorder correct. -- is how often -- they said out of these pain signals. About once a second or so. The problem is sometimes they're masked by wreckage -- -- be buried in sediment. And so was -- to -- is they are. -- can't even worse but. To actually find something don't know what about -- -- -- -- -- that from the from the device that detective is kind of a pain to the actual boxes themselves. We -- what kind of a search field is that. Well it. Sometimes you can get about five miles from the -- itself now you're working 23 miles deep you've lost some range there are so. Essentially you have to be almost right on top of this thing here on a good day. Now as you mentioned as the battery start to lose power. The distance the -- travels becomes less sensitive even closer to a -- -- -- -- And again as we -- as a for the manufacture guarantees that they will hold -- for thirty days but there is a possibility -- they can go beyond that correct. Correct we've seen the last sort of 45 days and actually very -- It happens that guarantees thirty days but they have gone longer and maybe we'll be lucky here -- If in fact Sunday comes and say for example both of those boxes stop pain. How does the search -- that. Well then you have to keep refining your techniques -- the airplane went hopefully you'll find some wreckage would help. And anything get into doing side scan sonar work instead of towing these devices -- more from -- pains you to -- -- different place. That actually does side scan sonar mapping of the ocean bottom and hopes to find the wreckage and that's how they found her friends for force. So possibly new technology that will be brought to the scene -- -- did that the investigation. Might actually grow in size. It could've -- of -- could shift you could see at some point they may. Dial back if you will on the aircraft -- being used to search of the things and may go to war ridges on the water search using sites -- sonar. Back to happen but once again -- is looking for the haystack because right now they're searching the best area. But -- -- not be that close we don't know former NTSB investigator Tom -- and aviation consult with ABC news we appreciate your time and in your insight and expertise. You can keep up with the story in real time by downloading the ABC news happened star -- this sort for exclusive updates on the go. For now though. I'm Dan -- -- New York with this ABC news digital special report.
This transcript has been automatically generated and may not be 100% accurate.