What's Next in Search for Flight 370?
LEMON: I'm Don Lemon. Our breaking news tonight, the data from Bluefin-21's first full mission is being analyzed right now, along with samples from the oil slick in the area. We will bring that information to you just as soon as we have it. Meanwhile, Australian Prime Minister Tony Abbott telling "The Wall Street Journal" the best leads will be exhausted in about a week. So, where does the search go from here? CNN's Jean Casarez has more.</s>JEAN CASAREZ, CNN CORRESPONDENT (voice-over): The sea has gone silent. More than a week after the last ping was heard, black box batteries are likely dead. With no evidence in hand, searchers for Flight 370 are considering their next moves.</s>ROB MCCALLUM, CNN ANALYST: We may not have all the clues, and we may have overlooked something.</s>CASAREZ: Australian officials say they will scale back the air search soon.</s>ANGUS HOUSTON, JOINT AGENCY COORDINATION CHIEF: The chances of any floating material being recovered have greatly diminished.</s>CASAREZ: But undersea recovery efforts may expand, if necessary, experts say, extending parts of the search area.</s>ROB MCCALLUM, OCEAN SEARCH SPECIALIST: I think that will involve retracing that initial arc of the suspected flight path, and that will require some very broad-scale sonar tools.</s>CASAREZ: Sonar even more powerful than the Bluefin-21 that can dive deeper and create even wider images of the ocean's bottom. It is still the best tool searchers have at their disposal.</s>MCCALLUM: Until we actually locate some debris with sonar, there's no point in bringing in remote-operated vehicles or manned submersibles. So sonar is going to be the tool of choice for the foreseeable future.</s>CASAREZ: It could be weeks, months or even years before debris from Flight 370 turns up.</s>MCCALLUM: My experience is that something always is found. Whether something is seen from a passing ship, something is spotted on a beach somewhere, along western Australia, there's always a clue that is unearthed somewhere along the way.</s>CASAREZ: The only option not on the table says McCallum, is to stop looking all together.</s>MCCALLUM: The entire aviation industry is underpinned by this drive for safety. And so until we know what happened to MH-370, we won't know how we can avoid this kind of tragedy in the future.</s>LEMON: That is Jean Casarez reporting. Thank you, Jean. I'm back now with my panel of experts. To Geoffrey Thomas in Perth now. You know, Prime Minister Tony Abbott told the "Wall Street Journal" that authorities would need to regroup and rethink their entire approach if they exhaust their leads this week and the Bluefin fails to locate MH-370 under water. What are they saying would happen next?</s>GEOFFREY THOMAS: I'm more guided by Air Chief Marshal Angus Houston, who cautioned us last week that this could be a long search. It will take us two months, approximately, to actually search the area of interest. So, I think three days in the underwater search, I think we should be guided by Angus Houston. A very measured man, very cautious man. He's done this before. And we're only on mission number three for Bluefin-21. I think we've got a little way to go before we start looking at Plan</s>B.  LEMON: He has been very calm, very direct and he doesn't overhype anything. Paul, is the reality that sonar is pretty much the only useful tool at this stage in the investigation?</s>GINSBERG: Well, I think so. It's also the safest. And as some of you, the other panel has already said, why risk someone getting into trouble before we know where we're going. And mind you, we're looking for a nickel, somewhere with on the Yankees stadium playing field in the dark. So we've got to find that first.</s>LEMON: Arthur, investigators continue to look into signs that the co- pilot's cell phone was turned on in the cockpit. And we have a tweet about this. This is from Bob. He says, "Is it possible that the co- pilot was trying to lay bread crumbs by turning his phone on to make someone aware of the plane's location?"</s>ROSENBERG: Yes, well, the issue with bread crumbs is some of them lead to the cheese and others don't. In this case, I'm of the mind that the cell phone hand shake with the cell phone tower when they overflew Pyongyang is actually very important. I analyze that in the context of the accident sequence. Beginning at 1:07 with the ACARS reporting. At 1:19 you have the final communication, "Good night. Malaysia 370." Two minutes later, transponders off. We're invisible. We turn around and fly across the Malay Peninsula. Also, importantly, the captain finally, we know, was reported as communicating, which means the co-pilot was flying. Now we have a co-pilot's cell phone handshake with the cell phone tower, a cell phone that should have been off. When you look at it in that context, I think it leads you to at least consider that the co- pilot or someone with his cell phone was reaching out. But of course, there are a lot of unanswered questions, 238 other people on board. Someone else's cell phone surely made the same contact. I think it is very significant.</s>LEMON: Remember, we were here until 1 a.m. Sunday in to Monday morning. And they were saying they were scaling back. There have 12 aircraft that are involved in this search, despite officials saying that they plan to scale back the aerial search very soon. It doesn't sound like they are winding down that search yet, does it?</s>TILMON: No. They keep talking about it, but nothing seems to change a great deal, and we see them going out yet another day. So I think they must have something in mind. Maybe something we don't know about?</s>LEMON: Well, could be true. Jeff Wise, as the search continues, one possibility is that civilian contractors could take a larger role and the military effort recede somewhat. If that happens, would that change the search, you think?</s>WISE: Well, I mean, as long as the resources continue to be committed, the search will continue. It really boils down to what information the authorities have, how confident they are that this investment of resources and material will yield results. And I think a lot of that will depend on what we find. As the prime minister said, I think the next week will be crucial. Because there is a fairly limited area on the surface that -- I'm sorry, on the seabed that corresponds to those pings. Remember, the towed pinger locater only had a range of about one or two miles, so it should be fairly compact. I think what the prime minister said is probably quite accurate. In the next week, we'll know where these resources should really be allocated.</s>LEMON: Mary, I have a quick question for you that's, you know, up your alley. How long will authorities continue with this active search operation? And will they stop at some point and have to make a decision on weighing the cost of a search -- of a search like this?</s>SCHIAVO: Oh, absolutely. They'll have to do that. And I do think they'll stop the above-the-water search very soon. But they're going to have to do that for a couple of reasons. One is just practical. They've got all these different ships and people and man power out there. They're going to get tired, in addition to getting expensive. And they're going to have to direct their resources to the places where they're really going to matter. And then then they'll have to broach the subject with the airline and the airline's insurer about how much of the rescue and recovery they are willing to pay for. And there have been cases where there have actually been suits filed over that.</s>LEMON: Wow. OK. When we come right back, my team of experts will answer your questions.