happening now, breaking news. the mystery of flight 370, a search aircraft detects what may be another signal from the missing jet's black boxes. the ping which officials say seems manmade as a sonobuoy is dropped in the search zone. sources say after the plane made the sharp turn over malaysia, it made a steep descent and disappeared from radar. so was that intentional? and investigators are now certain that they know exactly what are the last words from the

cockpit. good night, malaysian 370. and it isn't who they first thought. i'm wolf blitzer. you're in "the situation room." we begin with new clues in the search for flight 370, new details about its final moments. here are the latest developments. a search plane has recorded a possible ping from the airliner's black boxes. the signal was detected by sonobuoys that were dropped by the plane. analysts are studying the acoustic da acoustic data. sources say that flight 370 disappeared from military data after it shade the sharp turn back over the malay peninsula. they say this plane must have dropped in altitude between 4,000 and 5,000 feet. and as aircraft continues to go on another search for debris, our analysts and reporters are standing by here in the united states as well as around the world with the kind of special

coverage that only cnn can deliver. michael holmes is in perth, australia. let's go there first for the very latest. michael? >> reporter: wolf, a dozen of these sonobuoys have been spread around the search area, sort of an added tool, more electronic ears, if you like, listening for something, anything from malaysia flight 370. this time it was a search plane that picked up a possible signal from flight 370's black boxes. it happened near the same area where the "ocean shield" detected four electronic pings since saturday. aircraft have been peppering the search area with dozens of sonobuoys equipped with underwater microphones and they heard something. the sound they picked up has a potential of being from a manmade source and is within the frequency range of a flight recorder. but more analysis is needed. the air and sea search is intensifying as search leaders

grow more hopeful that they are closing in on a find. >> we are at this point much more optimistic than we were even a day or so ago and then certainly many more times optimistic than we were a week ago. >> reporter: the hunt for night 370 now focused on the smallest area yet. it's about 2200 square miles, or roughly the size of west virginia. that's about 25% smaller than it was the day before. and has narrowed dramatically from a few weeks ago. as investigators pour over the latest clues, cnn is learning more about malaysia flight 370's final moments. investigators now believe it was indeed the plane's captain, zaharie ahmad shah who said the final words from the cockpit, good night, malaysian 370." we're also getting a new

explanation of what happened after the boeing 777 turned west and crossed over the malaysian peninsula. malaysian sources tell cnn the plane disappeared from military radar for about 120 nautical miles, indicating that it might have dipped to an altitude between 4,000 and 5,000 feet. and wolf, a dozen planes and a dozen ships will again be scouring the ocean. the "ocean shield," the vessel that has been towing the ping locator has been joined by a british naval ship in the area where the pings were heard. it's called the "hms echo" and is trying to find signs of wreckage below. there are other ships, of course, a few hundred miles west where experts have been thinking any debris from the suspected crash site could have drifted over the weeks since the plane disappeared. wolf? >> still, they have not found any debris from that plane, have they, right? >> reporter: that's absolutely

right. they did find some suspicious objects that were spotted from the air as ships went over, picked it up but not related to the crash at all. there were a number of storms in recent weeks over that area where the plane is thought to have gone down and they have done all of these drift patterns and worked out the movement of the ocean and that's why those ships are all concentrated about 3 or 400 miles to the west of where they are looking for the wreckage because that's where they think ne debris may have ended up. wolf? >> very intriguing that they haven't found any debris at all. michael holmes, thank you. let's bring in miles o'brien and aviation analyst, managing director peter goelz along with former fbi assistant director tom fuentes. this latest suspected ping, if you will, miles, a fifth, if in fact it's serious, what do you make of it? >> well, it just adds to the case. we have a strong case that continues to build.

you know, i think the people heading up the search are reluctant to say we have the wreckage until they actually have eyes on it or virtual eyes on it. but as they build this case, the evidence grows and, more importantly, the box becomes a little bit smaller into which they decide to search and ultimately put on the bluefin device, the underwater vehicle that will go down and paint the surface with sonar. so it's very encouraging with the weather getting worse and winter ko winter coming, this is good news. >> peter, are you confident that they are getting closer and closer to one of the two black boxes? >> i am. five pings are better than four. ten would be better than five. they feed to keep monitoring this area and hope that the battery is continuing to provide power so we can pick up the pings. it's still a very large area, even though miles said, it's

much smaller but it's still off awfully big. >> what would you say, miles? >> i agree with them. let's hope that it helps locate the aircraft much more quickly. >> peter, barbara starr reported that the u.s. was sending a supply ship to the area to help the other searchers looking for some sort of debris from this plane. what do you make of the fact that they are bringing a significant supply ship in? it seems to suggest that they are going to be there for a while. >> oh, i think they are and i think they are getting ready for the long haul. even if they do get four or five more pings, once they drop the side scanning sonar device down, boy, that is going to be pain staking and long. so i think they are settling in for the long search. >> miles, what is your assessment? >> it just allows them to stay on site, wolf. given the distance from perth to get fuel and food and whatever,

that cou this is a crucial piece of equipment that the u.s. navy has supplied at just the right time and i think it's the perfect way that the u.s. navy can contribute at this point. >> because they are going to need it. i've heard anything, tom, and let me get you into this conversation. anything from days, weeks, maybe even months, even if they -- if these pings are the real thing to actually go down there and find one or two of those black boxes. >> that's right, wolf. i hope they are bringing their long underwear because they are going to be there all winter. >> you think it could take that long? >> it could easily because you're also going to have the search and then transitioning, hopefully if they locate it, into the salvage operation. so it's going to be a long haul out on the water. >> miles, that notion that the plane actually went down to 4,000 or 5,000 feet, the malaysian airliner, as it was exiting or going over malaysian

air space, if you will, could that have been literally flying under radar? >> well, it's a little confusing to me, wolf, because the terrain in malaysia offers up several peaks at about 7,000 feet above sea level. so if in fact he was flying at 4,000 feet above sea level, it's very likely he would have encountered what we call cumulus granite, which is what we call it in the pilot business which is a mountain. so an altitude above ground or above sea level, it's 7,000 feet, plus 4,000, which puts us at the 11,000 or 12,000, which we've already reported. these numbers have been very confusing to me and i'm told the malaysian military radar is not very accurate. >> what's your analysis of that, if in fact that plane went down to 4,000 or 5,000 feet, peter,

what's your asnalysis? >> well, i'm skeptical of it. this is the problem that the malaysians have had from early on in the investigation. they release unsourced information and then it's corrected days later. in this case, it seems awfully difficult for a 777 to drop down from 35,000 feet to 4,000 feet and then regain altitude in what would be 130 miles. that's a real feat of airmanship which i don't think occurred. >> do you think crews on the ground have that capability, if an airliner or a significant jumbo jet is flying over their air space at 4 or 5,000 feet, that they would miss it? is that possible? >> wolf, from day one they have given us no reason to have confidence in the accuracy of their radar or their diligence in monitoring their own radar and i think in this case we're reporting this as fact when it's

back-channel source information that's not been released officially from the government. so i'm suspect or skeptical like we all are about the whole thing and then i'm also skeptical, then, because once you accept this you're saying the plane did this, it went down, it was avoiding indonesia. they are attributing all kinds of motive to the pilot when we don't even know if the front end is true in the first place. >> i'm going to have all of you stand by. we've got a lot more to assess coming up this hour. up next, air crews are getting ready for a new round of search flights right now but in a new twist, sonobuoys dropped by planes are bringing dramatic underwater results. we'll speak with one of the search commanders coming up live. and investigators are now sure who was speaking in the last radio transmission coming from the cockpit. so what took them so long to find out? what impact will this have on the investigation? mine was earned in korea in 1953.

afghanistan, in 2009. orbiting the moon in 1971. [ male announcer ] once it's earned, usaa auto insurance is often handed down from generation to generation. because it offers a superior level of protection. and because usaa's commitment to serve current and former military members and their families is without equal. begin your legacy. get an auto insurance quote. usaa. we know what it means to serve. the expedia app helps you save with mobile-exclusive deals download the expedia app text expedia to 75309 expedia, find yours why relocating manufacturingpany to upstate new york?

i tell people it's for the climate. the conditions in new york state are great for business. new york is ranked #2 in the nation for new private sector job creation. and now it's even better because they've introduced startup new york - dozens of tax-free zones where businesses pay no taxes for ten years. you'll get a warm welcome in the new new york. see if your business qualifies at startupny.com frequent heartburn? the choice is yours. chalky. not chalky. temporary. 24 hour. lots of tablets. one pill. you decide. prevacid. ♪ 24 hour [ female announcer ] f provokes lust. ♪ it elicits pride... incites envy... ♪ ...and unleashes wrath.

♪ temptation comes in many heart-pounding forms. but only one letter. "f". the performance marque from lexus. but only one letter. hiwe just love scouring flea markets for special treasures. but with my type 2 diabetes, we now spend all our time at the pharmacy. with med-care, i don't have to! they deliver everything i need right to my door! with free shipping! plus, med-care takes private policies, medicaid, even my medicare! sleep apnea machines, nebulizers, med-care has all the finest medical supplies. the best part...med-care saves us money! med-care allows us the time to do the things we love. med-care. we deliver a better life.

an extraordinary new hint in the several for flight 370. a sonobuoy picks up what may be a signal from the airliner's black boxes. joining me on the phone is kevin mcevoy. air commodore, thanks for joining us. do you believe that this was, in fact, the fifth suspected ping from one of the two black boxes? >> good evening, wolf. it still requires further analysis but the understanding that we have from the chief coordinator is that there is potential for the ping to be

from a manmade source. so we've got our fingers crossed. >> how much battery life do you suspect is still left in those pingers from the two black boxes, the flight data recorder, the cockpit voice recorder? >> so the understanding that we have is that while it has a 30-day nominal life, the battery will still allow essentially a degraded signal strength. so we're anticipating that what we're receiving at the moment in terms of those pings from the coordination is that if they are manmade and they are coming from there, then there is still a very small signal strength. every day that goes on, the signal reduces. so we're very keen to make sure that the efforts that we're catching the signal that is there. >> are you dropping the sonobuoys into the water yourself as part of the new zealand mission? >> the aircraft dropping the

sonobuoys, those specific ones related to that specific equipment are only be dropped by the royal australian air force at this stage but we will have the capacity to do that but at this stage it's obama being utilized through the australian air force. >> so what is your responsibility, air commodore right now, what is new zealand doing? >> we have a p-3 orion in the search since the 15th of march. it's day 35 of the search today. we'll be going out again today. we're airborne in about an hour and we'll be going to the task area that we have to search. every day our crews are out there doing a search. it's roughly the size off the width of virginia. there's a total of nine going out today. so they will be very focused on the mission at hand and putting in another long, hard day to try and find some debris on the

surface. >> just to be precise, so far, as far as you know, and you know what is going on, air commodore, you have not found any, not even a tiny piece of debris from that malaysian airliner. is that right? >> we've found lots of debris but at this stage, none of the debris that we have found has been able to be linked to the missing malaysian aircraft, unfortunately. we'll continue that search today. the crews are motivated. the equipment is world class and we're very, very focused. >> is there an explanation that you have and your experts have, assuming that these pings are in fact pings coming from the black boxes, is there an explanation why no wreckage at all on the surface or anyplace else has been found? >> i mean, the underwater search is not my area of expertise. but what i can tell you is that between the two search areas in

terms of the debris and the potential wreckage, it's likely that they will be in different areas. so we'll go out, we'll put our crews and aircraft out in the debris area to focus on that surface, search for the debris. but it's still a long, challenging search. the search authorities are doing everything that they can to gather all of the credible evidence to try and join those dots. so to date from all of the crews, all of the nations involved and i'll be going out again today and continuing that good work. >> how much longer are you prepared to continue this air search? >> well, we are prepared to support the search for as long as we require and as long as the national government tells us that that's their priority. i've got no intentions of bringing the airplane home at the moment. as i say, we're rotating crews through to be able to potentially support a sustained

effort. so that's still a long way here, so to speak. >> and you say the air search is about the size of the state of west virginia. is that what you're saying? >> every day the several area that they search is about the size of west virginia. so it's a sizeable search area and that search area continues to either be refined, due to the ocean currents or the movement of that search and the potential debris field or as you've alluded to, the more information that we get, we can refine and go to the various areas. so there's a lot of search aircraft. there's nine search aircraft and three coordination aircraft up here today. a lot of ships in the area. we're very confident that if something is on the surface, our airline will find it. >> kevin mcevoy from the royal new zealand air force, good luck

to you and all of the men and women that are part of this massive, massive search. thank you. coming up, investigators finally know who spoke last in the cockpit and the voices not who they first assumed it was. sources say the airliner made a dramatic descent and for a long time effectively disappeared from radar. we'll tackle that mysterious development with our experts. ♪ [ male announcer ] when fixed income experts... ♪ ...work with equity experts... ♪ ...who work with regional experts... ♪ ...who work with portfolio management experts,

that's when expertise happens. mfs. because there is no expertise without collaboration.

we're getting stunning new clues in the disappearance of flight 370. joining us now is aviation correspondent rene marsh and justice reporter evan perez and law enforcement analyst former fbi assistant director tom fuentes. rene, let's start with the new information that we're getting on the last person to speak the final words heard from the cockpit to ground control. tell us about that. >> well, wolf, we are now told by a source in malaysia that it was actually the captain who spoke those last words, "good night malaysia 370" as it was leaving malaysian air space and going into vietnamese air space.

quite a difference from what we heard originally. before we were told by authorities that it was the co-pilot who spoke those last words. so now this changes things quite a bit as to who was on the radio and who was communicating in the air with air traffic control. we also know from this same source that it was five malaysian airlines pilots who were allowed to listen to the air traffic control radio transmissions to make the determination that it was the captain and not the co-pilot, as we had heard before, wolf. >> tom, what's the significance if it was either the pilot or the co-pilot who actually uttered those final words? >> wolf, everyone i've talked to has said it's really not that significant regardless, that the captain is in charge of that ship, he would make the determination, his co-pilot or first officer is flying for the first time without another chuck

pilot sitting behind him. if he decided to let him make the broadcast or take it himself, we're not true that it has any significance. >> what does it say to you, tom, that it's taken the malaysian authorities so long to discover this? >> this might not be as easy as it sounds to identify the voice. you have two individuals in the cockpit speaking in their second language. malay being their first language. and these are short, cryptic conversations. it's not a regular conversation with the tower. it's quick responses, short answers. ands a the plane moves further away, the radio may not be all that clear and they may be on a speaker phone situation in the cockpit. so there's a lot of factors that would make it difficult to tell exactly who is talking. >> tell us, evan, about the significance of the plane dipping. we've been reporting it went down, what, 4,000, 5,000 feet at

one point maybe to try to evade radar. what do we know about this? >> wolf, the investigators here in the u.s. are focused on trying to get as much information as they can about the people that were on the plane, obviously the two pilots they are very much interested in. they are not sure what to make about the change in the altitude. they don't know if it's definitive. it's certainly not going to be definitive until we can get some data from the wreckage at the bottom of the indian ocean and then they can go back to the information that we already have and determine whether or not this tells us anything. at this point it doesn't move the needle that much for the u.s. investigation. >> what does it tell you, tom, about this apparent drop to 4,000 or 5,000 feet in what may have been going on in the cockpit? >> the problem i have with it, wolf, is the whole concept that it made that drop. what authorities are saying is that we don't know what it did so let's assume that it made a

drop. we don't know if it exactly went around, that it didn't cross into indonesia air space. so let's say that it went around indonesia. these theories are being made on information that we don't have, not on positive information that we do. that would mean if the theory isn't accurate, who is saying what, taking the plane up or down or side ways becomes invalid. we don't know for a fact that that is what happened. >> we're also getting information, rene, as you know -- and this is 35 days or so into this disappearance -- that malaysian planes did scramble at some point after this plane went missing. tell our viewers precisely what we're learning. >> that's right, wolf. again, according to a source there in malaysia, these jets were scrambled as a precautionary measure on the morning of march 8th. shortly after flight 370 was reported missing. and again, this all happened or

this action happened before data was corroborated that the plane made the westward turn. that being said, we know that the transportation ministry sent out a tweet denying. again, this is information coming from the source that the jet was scrambled over the straits of malacca in the short time after this flight was reported missing. wolf? >> thank you. evan, you've been talking to your law enforcement sources. what are they saying to you about their anxiety right now? especially they are so determined to get at least one of those black boxes? >> well, you know, wolf, that is the key. and obviously the wreckage, to be able to examine that, the fcfbi is just standing by and waiting for the malaysians to come by and help. once the australians are able to get this wreckage, to be able to examine it and they can have

evidence teams go there and take a look at this. looking back at the passenger manifests and the crews and all of that stuff, they are taking the time that they have right now to examine all of that. but none of that really will solve this. they are waiting for the black boxes, for the wreckage to be found to put some light on what might have happened to flight 370. wolf? >> good reporting. stand by. up next, the u.s. is standing a key new tool to the search team. could that mean that they are t getting closer to finding flight 370? plus, the newest signal that is giving new hope thanks to this device we'll take a closer look at how all important new technology is right now. the day we rescued riley was a truly amazing day.

he was a matted mess in a small cage. so that was our first task, was getting him to wellness. without angie's list, i don't know if we could have found all the services we needed for our riley. from contractors and doctors to dog sitters and landscapers, you can find it all on angie's list. we found riley at the shelter, and found everything he needed at angie's list. join today at angieslist.com

how much money do you think you'll need when you retire? then we gave each person a ribbon to show how many years that amount might last. i was trying to, like, pull it a little further. [ woman ] got me to 70 years old. i'm going to have to rethink this thing. it's hard to imagine how much we'll need for a retirement that could last 30 years or more. so maybe we need to approach things differently, if we want to be ready for a longer retirement. ♪

first on cnn, a u.s. navy supply ship is joining the international task force. it will be used to replenish us a australian ships used in the search. our pentagon correspondent barbara starr is joining us now. she's looking into this part of the story. barbara, tell our viewers what you are finding out. >> wolf, the deployment of the chavez ship shows how long this may go on. they are going to need more help. the investigators have been on the sidelines for weeks while the search was going on but now that all may be about to change. as searchers potentially close in on finding malaysian flight

370, u.s. government intelligence, law enforcement, and aviation experts are quietly talking about what comes next. and at what point they will take a bigger role in the investigation. if new pings are found from the plane's black boxes. it could still take weeks to locate the voice recorder, which investigators hope will tell them what was happening in the cockpit. but it's the data recorder that may tell them the most about how the plane went down. >> it's going to tell you what switches were moved, when they were moved what your air space was, what your heading was. it's going to give you an entire picture of what that airplane was doing and when it was doing it. >> reporter: if debris is salvaged, more clues for the u.s. to follow. if part of the frame is bent outwards, it could indicate an explosion. if investigators find a punched-in nose cone, an

indication that the plane hit the water nose first. but still the question, what brought the plane down? and if it was a deliberate act, what was the motive? there has been no claim of terrorism found by the cia, fbi computer experts found no evidence of wrongdoing on the pilot and first officer's computers. malaysian sources say the plane may have deliberately dropped to a low altitude, attempting to avoid radar. that low altitude could be one of the biggest indications flight 370 was not having mechanical trouble and trying to avoid other aircraft for safety reasons. >> did you hear anybody say that there was any emergency call? why would you turn off the transponder? >> and so at the end of the day now, u.s. officials still theorize somebody steered that plane away from land and they still need two answers.

who did it and why. wolf? >> barbara starr at the pentagon, thank you. let's bring in our aviation analyst, miles o'brien, peter goelz. those questions have been with us for 35 days. a supply ship is on its way to help out. the search is going to obviously continue. they are not ready to give up hope, by any means, especially now that they've had four or maybe five pings from what they suspect are the two black boxes. >> yeah. if you had to put a number on the hope, the numbers are going up on the hope as the pings come in. that not only provides more confidence in the right place but also narrows the location of a potential search with that underwater autonomous vehicle that can use sonar to more or less paint the surface or the bottom of the ocean and give a picture of what might be there. the wreckage will become very clear. it will take time to do it and

that's why you want to get as many of those pings to box off the location where you would ultimately put that unmanned vehicle in. >> you used to do these investigations, peter, at the ntsb. if you were involved in this one, is there anything that you think you would need as an outsider that they are not getting right now? >> no. i think the investigative team and the search team has got every piece of equipment that they need. they've got everything that they've asked for. what they need is a little luck and they need those pingers to keep working for another week or so. >> miles, i suspect you want more, though. you would like everything they are doing right now but even more, right? >> well, as far as resources on the scene, i think right now it's one of those situations where you don't want a lot of people near where that pinger is because you want it quiet in the ocean. and so it's kind of counterintuitive. at this point you want resources to back off, let them get as many pings as possible and once you get an identified area of coming in and then it turns into

a different kind of scenario where you've identified where the wreckage is, then you have to get another kind of vehicle on to the wreckage and then you have to get that vehicle to find these precise location of that cockpit voice recorder, the flight data recorder and retrieve them. it's going to take a long time to get those to the surface given all of the steps that are involved there. >> you think, peter, this fifth ping that the australians picked up is the real deal? >> well, i think we've got to go on the understanding that it likely is and let's hope that they find some more today and tomorrow. they need, as miles said, to narrow this situation down. they are saying that they are searching the area, the size of west virginia. let's get it narrowed down to the size of lower manhattan or something so they can really start to put the resources into mapping the bottom of the ocean bed and finding the wreck ablag. but to do that, they've got to

get a number of more pings. >> the air search is the size of west virginia, looking for debris approximately in the size of west virginia. miles, the four pings that they discovered, that's in an area that is two or four miles deep but 17 miles across. that's a lot smaller than west virginia. it's the size of lower ha manhattan. >> the size that they are honing down on is where the pings are, that's a smaller area. and then the larger area is the debris. it's a complete mystery to those of us who have any experience with covering these sorts of things or actively engaged in these investigations. the fact that they haven't found any debris is just extraordinary. now, they are using ocean currents and predictions about where the debris might have drifted from the location where these pings are located and that's what gives them this area the size of west virginia. hopefully they will find

something floating there. >> guys, stand by. there's a lot more coming by. just ahead, a possible black box ping detected by a sonobuoy which was dropped by an aircraft. we're looking at the latest high-tech clue in the search for flight 370. co: sometimes you don't know you need a hotel room until you're sure you do. bartender: thanks, captain obvious. co: which is why i put the hotels.com mobile app on my mobile phone. anyone need a coupon? i don't. why relocating manufacturingpany to upstate new york? i tell people it's for the climate. the conditions in new york state are great for business. new york is ranked #2 in the nation for new private sector job creation.

and now it's even better because they've introduced startup new york - dozens of tax-free zones where businesses pay no taxes for ten years. you'll get a warm welcome in the new new york. see if your business qualifies at startupny.com that's a good thing, but it doesn't cover everything. only about 80% of your part b medical expenses. the rest is up to you. so consider an aarp medicare supplement insurance plan, insured by unitedhealthcare insurance company. like all standardized medicare supplement insurance plans, they pick up some of what medicare doesn't pay and could save you in out-of-pocket medical costs. call today to request a free decision guide to help you better understand what medicare is all about and which aarp medicare supplement plan works best for you. with these types of plans, you'll be able to visit any doctor or hospital that

accepts medicare patients... plus, there are no networks, and virtually no referrals needed. there's a range of plans to choose from, too, and they all travel with you anywhere in the country. join the millions who have already enrolled in the only medicare supplement insurance plans endorsed by aarp... an organization serving the needs of people 50 and over for generations... and provided by unitedhealthcare insurance company, which has over 30 years of experience behind it. ♪ call today. remember, medicare supplement insurance helps cover some of what medicare doesn't pay. expenses that could really add up. these kinds of plans could save you in out-of-pocket medical costs. you'll be able to choose any doctor who accepts medicare patients. and there are virtually no referrals needed. so don't wait. with all the good years ahead, look for the experience and commitment to go the distance with you.

call now to request your free decision guide. this easy-to-understand guide will answer some of your questions and help you find the aarp medicare supplement plan that's right for you.

as the underwater sweep continues, another possible signal from flight 370's black boxes has been picked up from a sonobuoy dropped from an aircraft. our brian todd has been looking into these high-tech devices.

>> wolf, teams are stretching the boundaries of this technology and they have done it again. the latest signal came from something designed for maritime combat, not search and recovery. they are dropped out of a plane and descend below the surface, open up their payload and hunt for their target. these are not bombs or torpedos, they are called zosonobuoys. >> they deploy a hydrophone. >> a source tells cnn that sonobuoys were dropped from an australian pc-3 orion plane. >> it has saltwater switches that starts activating different deplo deployments. there's a bunch of gear in there. some of it floats to the surface so there's a radio antenna that talks to the aircraft and they

are in constant communication and the microphone, the hydrophone is listening below the canister. >> the australians got this batch from american manufacturers, sent a cargo plane to indiana to pick up more than 1,000 sonobuoys. the device was first deployed by the u.s. navy but this is one of the tools the navy has to look for and track enemy submarines so they're under the ocean surface, don't have a radar signature and need to use sound in smart ways actively and passively to find them and then track them. >> reporter: on this mission the sonabuoys and the orion planes have been modified to detect sound in black box pings. sonar operators on board the as aircraft are monitoring computers. sonabuoys are dropped in a pattern, 84 at a time. they're durable. >> the beauty of these thing,

the sonabuoys, once you put them out they stay out there a long time, up to eight hours. >> reporter: thenthy they expi and sink to the bottom. while deployed the sonabuoy can go 1,000 feet down. how can they detect signals possibly from a black box as far down as 14,700-plus feet? the sound moves through the water in a manner it could be detected further away and with good weather, signals are a lot easier to hear. wolf? >> interesting stuff. is there any chance these sonabuoys could possibly go deeper than 1,000 feet? >> possibly. they're confident the technology has been tested at a much greater depth during this entire operation. you can surmise they're going to try it get it down further. they want to cover as much water underwater, as much of the area as possible. they need to max out the use of these sonabuoys. >> yeah. time quickly running out as well for those batteries on those two black boxes. thanks very much. coming up, crews are racing

against the clock to catch those final pings. will they reach the wreckage before the black box batteries run out? and the president as we rarely see him. his emotional address on race, the civil rights act, and president lyndon johnson. >> thank you. [ male announcer ] when fixed income experts... ♪ ...work with equity experts... who work with regional experts... that's when expertise happens. mfs. because there is no expertise without collaboration.

we have much more on the search for flight 370 coming up. first, other urgent stories we're following. li police are searching for answers one day after a 16-year-old suspect went on a rampage at a pennsylvania high school. alex hvibal. the mass stabbing in a quiet pittsburgh suburb. police seized the suspect's computer and cell phone but no word yet on a motive. obamacare numbers are climbing even higher. 7.5 million americans are now enrolled in the federal or state exchanges. that's up 400,000 since april 1st when the administration announced it passed its target of 7 million.

the numbers are a surprising victory for the president after the federal website's disastrous rollout made for a slow start. the house oversight committee is charging a former irs official with contempt of congress. lois lerner refused to answer questions for the republican controlled committee by pleading the fifth. she's accused of blocking conservative groups are tactics and status for political reasons. democratic members argue the investigation is a witch hunt and political stunt. the contempt vote now moves to the house floor. president obama is in austin, texas, today celebrating the legacy of president lyndon johnson. and marking the 50th anniversary of the civil rights act. in his speech, the president got emotional. praising the longtime texas senator for using his political capital to pass major laws and becomes an unlikely hero in the civil rights movement. >> the ability to connect his experience with the brown child in a small texas town.

the white child in appalachia. the white child in wise. as powerful as he became, in that oval office, he understood them. he understood what it meant to be on the outside. and he believed that their plight was his plight, too. that his freedom ultimately was wrapped up in theirs. and making their lives better was what the hell the presidency was for. >> the president also noted that the landmark civil rights legislation helped pave the way for him. as the first african-american president. coming up, special coverage of the mystery of flight 370. air crews are preparing for takeoff after another possible ping from 370's black box. could this be the day? the "situation room" continues

in f 60 seconds.

happening now, our special coverage of the mystery of flight 370. air crews are about to return to the search area where another possible signal from the jet's black boxes was detected. are they getting closer to finding a crash site? we're learn new details, including maneuvers that may have been intended to dodge military radar. plus new confirmation the final message from the cockpit to the tower was spoken by the captain. we'll break down all the new information and what it means for the investigation. we want to welcome our viewers in the united states and around the world. i'm wolf blitzer. you're in the "situation room." >> this is cnn breaking news. we're following several breaking developments in the flight 370 mystery. right now, experts are analyzing what could be the fifth signal from the missing jet's black boxes. planes are about to take off