>> you wait five hours and give up. thank you for watching, we'll see you tomorrow night. anderson starts right now. good evening, it is 8:00 p.m., off the west coast of australia, 8:00 a.m. and off the coast, a sub is finally back on track, tonight you will see for yourself exactly what a bluefin can see. also, what appears to be the biggest gathering of al-qaeda, we'll tell you who is in the video and why it is so important. and later, our own dr. sanjay gupta suits up to help fight the ebola outbreak in west africa, some of whom have lost lives in the battle. some of the medical personnel. we begin with dr. sanjay gupta. and right now, a bluefin sonar scanner is deep in the

ocean trying to do the job. as you know, the mission was aborted after nearly six hours, today, the round is expected to go for hours, there are new developments, the developments with the oily substance, and a tracking element that may change everything about what happened to flight 370. the question is, why six years later will it be rolled out? first, michael holmes from perth. what is the latest, michael? >> reporter: anderson, good morning from perth. yeah, the bluefin-21 doing its work down under, it is almost half way to the ocean floor segment, two hours to get up, 16 hours on the bottom. then they download the data. also planes and ships out there again today. we had been told that that phase of things looking for surface wreckage would be scaled down

this week. but no sign of that yet. they are still in the air and on the ocean looking for any wreckage. of course, none found so far and we're now into our sixth week, anderson. >> as you say none found so far, the wreckage. has the data been processed from the bluefin's first dive, as we know it was called off because of the depths. do you know if they have found anything of note? >> reporter: yeah, good question, in the last hour we got word of that. it covered about four square miles during the aborted mission. on the normal vision it would cover half or 40 square kilometers. they analyzed that data. and sad to say they found almost nothing of any use, nothing relevant. but of course it was just the first mission, and an aborted one at that. >> and the fuel recovered from the search, do they know if it is related to the plane?

have they been able to determine it yet? >> not yet, we have to remember the search area is about over 2,000 kilometers off the coast of western australia. they did pick up the two liters of oil that they found floating out there near where the ocean shield is. they have bottled it. basically what they have to do is get a ship out there and then helicopter it to the ship and the ship can get it closer in. and then helicopter it to get it to perth. they say it will take two or three days so we'll know what it is. they have sent samples of the engine oil that would have been in mh-370's engine so that they can do a comparative analysis on that. they're also going to be check to see whether it could be hydraulic fluid. yes, just getting it back here will be a journey. >> all right, we appreciate it. and bringing back david souci,

cnn analyst, david gallo, co-leader of the search for air france flight 447. also former director of transportation. mary schiavo. david, the fact they didn't get any data from this bluefin, i don't think you would be surprised. >> it is frustrating, unfortunate to think something went wrong but it is not unusual. >> the fact the mission was aborted because of the depth, they found themselves in deeper water than they anticipated, the surface was deeper and they had to call it back and sort of re-calibrate things. does that indicate to you a lack of real understanding of what the depth is here? >> well, every day they go out there they will learn something new about the terrain and make

adjustments, both to the hardware of the vehicle, the software, and the plans. it may happen once or twice more. we had it aborted once or twice with the search for air france 447. >> why did it happen -- >> we had the remis 6,000s, the approach was different, they were going with -- as captain matthews talked about the tactical approach, which the idea they had the solid pinger location, they were going to throw the dart at the bull's eye. our idea was covering it with multiple vehicles so it was a totally different kind of mapping program. >> david souci, do you think that indicates they have perhaps more information that they let on? >> that is the way i'm seeing it. apparently they have more confidence on where it is, or as

like david said they would throw it more at the screening. >> they do, david, have another underwater vehicle and go deeper? >> they have plenty of tools that they can bring to bear on this. if they need to change strategy, maybe the tactical means is not working and they have to go to more strategic -- they will bring something else in on the mission. >> and mary, we heard from the air marshal angus houston, the air search is nearing its end. that is not certainly something the families want to hear. >> well, that is true, but at some points the currents will work on the debris that would have been there almost five or six weeks. and there is just not a real chance they will find much at this point. this far out it would be so far dissipated. and they can't justify it. particularly as the other guests have said they really believe they have zeroed on the point where the plane is. and there is, of course, all the

many stories floating around about australia's incredible radar, almost mythiccal quality, they do have strategies, throwing the dart where they think the bull's eye is. >> it is kind of amazing that the plane can theoretically hit the water -- i guess there was the ship? >> the sidney. >> and only a raft went down. >> and later, near christmas island, the site, one life raft showed up. >> it is incredible. >> absolutely incredible. >> we heard the malaysian transportation minister, david souci, that it matters less who takes control of the black boxes as long as the black boxes are found. to you does that matter who takes control? >> that was a little disturbing to hear that. it doesn't matter who takes control. it matters a great deal. he is in charge of this investigation, by the rules

nothing goes there until he says it goes there. so he is responsible of making that decision. i would think of anybody he would care where it goes. >> mary, we also heard the malaysians saying they're setting up a committee to look into how the plane could vanish without barely a trace, is that what should happen at this more? >> well, that, plus more. when we do an investigation, the ntsb, they set up similar committees, except far more. so it is good they're setting up the committees. but the true investigative committee that should be working overall to solve this accident, the causes, the probable causes, any recommendations, the full panoply of what comes out after a crash really should contain far more working groups and committees. but yes, if they're going to be very objective and look at how this happened. look at their own response and how it happened, of course it is good to do that. >> a lot to cover tonight, including as we mentioned, underwater territory that we've

never seen before. also, vladimir putin's words, on paving the way for civil war. let us know what you think. coming up next, david gallo shows us the amazing look of what the ocean floor looks like. two underwater sonar devices and the remarkable pictures the machines can take. and later this. 797, over on the -- may day, going down. >> we're going to show you what begins as a disaster becomes an opportunity. air crashes over the years that have made air crashes today so rare. lessons that have been learned and what is being learned this time when we continue. it's built to be as fast o as it is strongadvil. and fights pain at the site of inflammation. and made for people like paul, who believe nothing should stop

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al-as . with the bluefin back under water, search teams will get not only a better chance of finding pieces of flight 370, they will also get a better look at the lay of the land on the ocean floor, the nooks, the crannies, and the ocean floor. back with me is david gallo, we have two images, clearly two different ships. what are we looking at? different depths? >> the more i look at it, the more it looks like different depths. this looks like a mass up here -- >> this would be amassed up

here? right there. >> so it is the kind of image the bluefin can take of objects on the sea floor. >> it is just remarkable. can you get it in one pass? >> you can get it in one pass, it depends on how close the vehicle is in the water, it can be one pass or multiple passes. >> i want to take another look at a side scanning sonar -- >> yeah, this is fantastic. this is the path of the vehicle. so the robot is heading in this direction sending out pings to either side like this. and the sound comes off and bounces off objects. when you see something like this, bright, it means that is a hard return. there is a shadow sounded. you can see the ship over the top. it leaves a gap directly underneath the vehicle, why they call it a side scan or a side-looking sonar. >> and when you get an image like that, it is actually two

images -- >> two beams, the portside and star board side. >> and you want to look -- not from a bluefin, but a search you were involved in. this is actually the titanic? >> yes, the path of our vehicles are mowing back and forth. >> you can see lines in the image itself. >> exactly, right, and so many, many images. that is over a mile across. this is the bow of the titanic sitting right here. it broke in half, this is the stern of the titanic, it broke away, so this is six football fields. all the debris field, all of these things you are looking for, from pieces of pottery and lights -- all of these things, little speckles. the stern had the huge debris field associated with it. >> there is another titanic

image here that i want to look at. is this zooming in on the bow? >> yes, just zooming in on the bow. this shows you how powerful the sonar can be, jack was king of the world, the mask, some of the openings here -- >> you can get this just from one pass? >> just one pass. and sometimes we go over it two or three times to make sure we don't miss anything. >> what kind of vehicle took this? >> this is the remis 6,000, very similar to the type of vehicle that the bluefin-21 is. >> so it goes 6,000 -- >> it goes deeper, so it is incredible work. >> this is another image of the titanic, extraordinary. >> this is an optical image, many, you can see the sides of the image -- >> so this is multiple photographs. >> this is done with another vehicle operated by phoenix international that may or may not come into play later on in the malaysian air search. so this is the optical view of

that same bow. >> so that is an underwater vehicle that just -- >> moves along the side of the ship, click, click, snap, snap, anyone with a digital camera that has done that panoramic view knows how hard it is to do that. >> it is just incredible, the technology, for all the bluefin-21 can learn it is only there to take sonar pictures. there will be other searches, done with other vehicles. gary tuchman found out more on the pieces of the shuttle challenger. here is what he saw. >> reporter: at first glance, it looks like a spacecraft more than anything else. but this is a research sub that combs the seas doing everything from medical to ship recovery. >> we have multiple light systems on the ship.

>> reporter: jimmy nelson used to spend about 170 days a year on this sub. the johnson ceiling submersible, as it is known. it is now retired, the florida oce oceangraphic institution. but other manned sea vehicles might be next the line to aid in the malaysian airline search. >> if this can get to the wreckage is, how effective do you think it can be in the recovery effort? >> very effective. >> reporter: this is the view of the submersible in the atlantic ocean. it can go 3,000 feet deb deep, like all vehicles it can only go so far. this recovered some of the wreckage from the ill-fated shuttle. >> we have the capability of moving around. >> reporter: a tool called the

manipulator does the important work of grabbing, scooping and sucking up samples that are recovered. this sub is about 24 feet long and 11 feet tall. it weighs about 28,000 pounds. it has enough oxygen, and emergency provisions on board for the people to survive under water for up to five days. >> reporter: there is also a back cabin on the submersible. a crew keeps an eye on the submersible. and another sub shares the area, about 5 x 3 feet. >> so to give the viewers how tight it is. this is how you're sitting. this is how i'm sitting and you could be here for hours. >> reporter: but during those hours this is what is taking place. >> so we fire up the sonar system and it does a sweep and paints a picture as it spins around 360 degrees. if there are solid targets it

will paint a small picture. >> reporter: the use of high-tech unmanned underwater vehicles is increasing. but jimmy nelson says when looking for wreckage, the manned submersibles offer an important dimension. >> so you can see that looking out of the corner of your eye, it can spot things that other manned craft can spot? >> correct. >> reporter: others may soon be sent to action in the indian ocean under water in an effort to solve a mystery. gary tuchman, fort pierce, florida. >> for or information you can go to cnn.com. coming up tonight, could a new system for tracking systems with gps prevent this type of thing from happening again? the question is, if it can help why isn't it being implemented right now. and elsewhere, making sure the saddest moments in aviation history never repeats itself. also breaking news, a new

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. the crash of flight 370 and the mystery surrounding it understandably scares everybody. the fact is, though, your drive to the airport is many, many more times dangerous than the flight. and there is a reason for that. the business of making planes, and carrying passengers, and the industry is still a very much

tight-knit community with a long tradition of learning from past mistakes or like this one, anticipating them. they have the use of gps technology and satellites instead of radar. requiring that all aircraft operations in the u.s. be ready for it with the right transmitting equipment by the year 2020. and it is precisely the type of situation that could have helped follow and find flight 370. and in so many situations, the result of a lot of hard lessons learned. >> the flight from miami to atlanta, the day before mother's day, 1996. the pilots hear a loud boom six minutes into the flight. >> returning to miami. >> what kind of problem are you having? >> smoke in the cabin. >> the pilots head to the nearest airport. meanwhile, passengers are yelling about a fire. the aircraft rolls on its side, then crashes nose first into the

florida everglades, killing all the people on board. the ntsb believes it happened in the cargo department. >> if we would have had this type of element, it would have been afforded more time to get the plane back on the ground. >> the faa took those words to heart, and as a result changed standards for cargo, requiring smoke detectors in the cargo holds. >> and fire distinguishers. and in canada, the plane made an emergency landing on the way from dallas to toronto. there was a fire in the bathroom. >> we have a fire in the bathroom and filling up with smoke right now. >> reporter: incredibly, the plane landed safely. but half the passengers and crew died because they could not exit the plane fast enough. that gave rise to new fire safety standards, including

bathroom smoke detectors and automatic fire extinguishers. today, planes are much more fire resista resistant, with chairs and carpets more fire resistant, and the flight exits pointed to before takeoff, those were added to save your life, too. smoke in the cockpit was the problem on swiss air flight 111 after it took off in 1998. >> we have to land immediately. >> it crashed just off the coast of nova scotia, they traced the flight back to the entertainment system. following the crash, the faa ordered all mylar replaced with

fire resistant materials. >> we are calling for better standards in the industry. >> reporter: in 1995. we saw a huge improvement in technology to protect us from high winds after delta flight 191 crashed at dallas/ft. worth international airport. it was landing during a thunderstorm, 137 people died. after much research by nasa and the faa, forward-looking window sheer radar detectors became the standard. the flight out of jfk airport in 1996 was another hard lesson. >> it blew up in the air, and then we saw two fire balls go down into the water. >> reporter: the ntsb determined an explosion in the fuel tank caused the crash, blaming it on a wire that short-circuited. the faa later mandated changes to reduce sparks from faulty wiring. randi kaye, cnn, new york.

and joining me now, author of why planes crash, and les amend. les, does it seem like changes only occur after a tragedy, but -- >> dave will agree with me. this is called tombstone technology? >> tombstone technology? >> yeah, when something tragic happens then the changes occur. it is traditional for the ntsb and the faa to be at odds once the regulatory agency finds there is probable cause on what happened. >> you agree with that tombstone technology? >> yeah, it is a term that has been used. and that is what the faa has been walking away from, over the last years, the airplane matter was not just a cause of having it fixed. as they get more complex you

have to look at the interrelation between the systems and understand ahead of time and look for precursors. >> and with the gps system that they will have in place by 2020, would that have made it much easier? i mean, if it was in the area for flight 370 to track it? >> yes, absolutely. the certification process said we need to change how we do things, including the air traffic control system. the next process that came out, they would have information constantly about every other aircraft that may even cross their path. >> would it still be possible, les, if a pilot or a co-pilot were able to make a plane go missing, would it still be possible to do that, to make a plane go missing? >> well, dave and i talked about this new system, the

satellite-based system. the airplane regulates the system, they send it to a satellite system, the ground system sends it to air traffic control. this is what i use in the atlantic, it is mandated across the atlantic and also in europe. could it be turned off? dave and i discussed the technology that the transponder doesn't have an effect on it. i have to verify that. but to the best of my knowledge at least on the triple 7 you have to turn off the flight management computer in order to disable that system. >> you agree with that? >> yeah, i do, the point of this system is that it can't be turned off. the beauty of it, is everybody is interlinked, if it goes off, all the alarms and bells and whistles go off. saying there is an aircraft out there. all the planes, their flight plan is mandated by knowing where everybody else is. >> it is in europe also at this

point. mandated in europe but the problem is you have to get the air traffic control people to comply with the system or buy into the system. so the malaysian airline, that part of the country or world may not be subscribing to that system. >> again, all of this technology is really fascinating. i mean, it is one of the things about what happened to flight 370, i think the viewers and everybody is learning a lot more stuff about aircraft than any of us even know. david souci, and les amend. appreciate it. plall right, coming up next the largest gathering of al-qaeda believed to have been held. also, dr. sanjay gupta with more on the efforts to stop the deadly ebola outbreak. and when you put them in charge

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. breaking news out of boston, this is video of an area near the boston marathon finish line on boylston street. we're not showing you live video.

the boston police asked us not to show live images, the bomb squad dealing with what they say is a pair of backpacks. they don't know what is in them. a robot is on scene. police say they have a man in custody, we don't know too much about it. police say the two backpacks, again, they do not know what is inside them. clearly, police have the area cordoned off. the bomb squad is on scene, we'll continue to follow it. and more on possible new plotting by al-qaeda. it surfaced recently on jihadist websites, showing a top al-qaeda leader addressing more than 100 followers in yemen, telling them he wants to attack the united states. the u.s. officials were not saying if they were caught off guard and didn't know about the gathering or couldn't get a drone there to strike it. barbara starr has more. >> reporter: barbara, the video is really amazing, the number two al-qaeda leader out in the

open, talking to about 200 of his followers. >> isn't it extraordinary? this is the area in yemen that they consider the most dangerous stronghold. they promised to attack the united states directly yet again. and yet 100 of them, including this top leader and other leaders are able to openly gather and have a meeting and talk and maybe propaganda. it may be recruiting, but it is also sending a message to the united states we feel strong enough and secure enough that we can be out here in the open and we're not afraid that you're going to attack us. so it is a real message. >> i mean, there obviously have been a number of drone strikes, some effective in yemen, do we have an idea when the video was taken? >> well, actually, the u.s. intelligence community believes it was taken weeks ago. because the top leader, nasir

al-wuhayshi, is greeting several men that al-qaeda broke out of prison this past winter. and now, they are free. and he is trying to recruit them into his movement even further. so they believe it was actually in the last several weeks because of that tie to the prison breakout. >> do we know how many assets or what sort of intelligence we actually have about these groups in yemen? i mean, was the u.s. aware of this gathering? >> well, this is the absolute critical question right now. did the u.s. know about it, or is the intelligence about yemen right now so spotty that they did not know? one of the things that concerns the cia, the white house, the pentagon the most is this al-qaeda group has gone underground in its communications to a large extent. they are staying off the internet. they're staying off cell phones. they have gone back to using couriers a good deal because they are afraid of u.s.

surveillance of the u.s. intercepting their communications. so this sort of going dark, if you will, is one of the big concerns that the u.s. may not know as much as it wants to about what this group is up to. and didn't know that 100 of them were out there meeting in the open. >> fascinating, barbara starr, thank you. >> sure. i want to bring in national security analyst, peter bergen, period of ti peter, what do you make of this? >> this guy is the number two in al-qaeda overall. it doesn't appear from this video that there are any civilians in the sequence. they wouldn't take a shot if there were civilians in the area. but these all appear to be members of al-qaeda. this guy is the number two in al-qaeda worldwide. to me, it doesn't make any sense that they wouldn't take the shot if they had it in their sights. >> it is also -- i mean, this is a group that has been very careful about its

communications. given that, why would they make a video about this and then have it out there? >> as barbara said, this group is relying on couriers. they know from stories in the past that their electronic communications were intercepted. that is why we had a lot of u.s. embassies closed last year as a result of nsa intercept. so this sort of flies in the case of being careful. so clearly they felt they could do this with some impunity. >> and clearly, they thought it had a type of propaganda value, again, a show of display or strength. there are people we don't see in the video. the bombmaker, correct? >> yes, he is a man who -- >> al-asiri, correct? >> yes, he has really gone dark. he is very, very hard to find. at the end of the day this guy is more important than anybody

else. because he is the guy that can build bombs on planes that are undetectible. unfortunately, he may have trained other people to do the same thing, we do not see him here. >> and as barbara said, people broke out of prison in the big prison break in yemen. >> well, i think, anderson, they controlled big chunks of yemen in 2007. they actually have taken a lot of hits. for starters, there have been a number of drone and cruise strikes since president obama took office. this videotape actually indicates that they feel the pressure is off. but for the past couple of years they have been under a great deal of pressure. >> peter bergen, appreciate your help. and just up, vladimir putin is saying something that sounds a lot like what he said about crimea. plus, dr. sanjay gupta has more on the attempts to stop the spread of the deadly ebola

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new developments tonight in the ebola outbreak in the western african country of guinea, our own dr. sanjay gupta is there, reporting on the

efforts to contain this mysterious and deadly virus. now in the last few weeks, at least hundred people have died, 14 of them health care workers. there is no cure from the ebola virus. what has caused concern it has reached the capital of guinea, close to the airport. >> reporter: you're about to go inside an isolation ward in guinea. there is a reason you may not have seen images like this in the world before. these patients are fighting one of the worst diseases in the world. it has disarmed their immune system and invaded their organs in their body. up to nine out of ten patients will die. but this horror is isolated in conakry, guinea, we found markets full, children, lots of children still smiling. you see as scary as ebola is, it

is not particularly connotatita. people don't typically spread it until they're sick, really sick. when that is the case, patients are not usually walking up and down the streets, they are down in beds, in hospitals or even worse. even the dead are highly contagious. this doctor from the cdc has helped to trace the ebola outbreaks for more than 30 years. >> this risk is not the people dealing with the ebola patients, it is dealing with regular patients not thinking of ebola. >> you see it only takes a small amount of virus on your skin to spread the disease. nothing is too careful for them. tim gagatek is a doctor from canada who comes in for weeks at a time. he is not married. he has no children. that would be a job liability, he tells me.

multiple pairs of gloves and masks, the head is completely covered. a multi-layer gown, boots, then an apron. it is positively suffocating in the 100-degree weather. prepares to help a patient with ebola is like preparing for a visit from somebody from the moon. they do this so people outside the wards, the people on the streets will never know what it is like to be inside. >> sanjay joins us, now, the number of people, the death toll is going up. but the government says it is nearly under control. can both be true? >> reporter: well, you know what happens in these situations a lot, anderson, initially there is some confusion as to whether this is ebola or not, you suddenly get a lot of cases as

people realize, previously sick people had ebola. so the numbers are still going up. the rate at which they are going up has slowed down a little bit. but it is important to report sometime from now, a month and a half before you can even say the outbreak is over because of the incubation period. >> it is incredible to see the video you shot. to see inside, i feel for the patients there. it must be so terrifying. a, to know the mortality rate of this, to have the doctors and nurses to be completely protected in gear, which of course they have to be. it has to be so terrifying or isolating. when will they know or how will they know when the outbreak is over? >> yeah, it is amazing, imagine somebody has a headache, fever, joint pain. they end up getting tested for ebola. and the next thing they know, they're in the isolation ward.

and the next people they see is the reality there, the people dressed as they are. the way they figure out when the outbreak is over, because the virus can incubate for a period of time, up to 21 days they say, before someone might show symptoms, the general rule of thumb is they wait two incubation period, for 42 days, if there are no new cases, they say the outbreak is over. that is typically how they measure the outbreaks. >> and you were in cameroon doing a report on the virus, and there is still so much we don't know about this. we don't know where the reservoir for this is, where exactly it comes from. >> reporter: it is so fascinating, such a medical mystery. they don't know. and just to give you a little bit of an idea of the process where they -- where the outbreak

occur occurs, the virus hunter's will go in there and capture hundreds if not thousands of animals, trying to find the ebola virus, what are known as antibodies, the response to the virus, anything, any kind of clue. they sort of think the fruit bats may be the reservoir, but after nearly 40 years, anderson, they still have not confirmed it or proven it. >> wow, sanjay, we appreciate you being there. and for more information on the doctors and how you can help to fight the virus, go to cnn.com/doctors. and oscar pistorius, reading a valentine's day card written by his girlfriend, one she never gave to him because he killed her, when we return. [ woman ] i've always tried to see things from the best angle i could.

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update on breaking news out of boston, we just learned the bo boston police just moments ago destroyed one of two backpacks. we don't know whether that bag or the other one contained anything dangerous. the detonation happened without incident. the area is blocked off. and the police say they have a suspect in custody. anderson, ukraine launched its first military action against pro-russian separatists,

a day after they ignored a warning to lay down their arms. meanwhile, russia's president vladimir putin warned them. and oscar pistorius at his murder trial, the disabled athlete testified that he didn't consciously pull the trigger the night he shot and killed his girlfriend, reeva steencamp. afterwards, the defense had him read a valentine's day card that reeva gave him. and charges filed against the suspect in the killings of three people near kansas city, he could face the death penalty under one of the murder charges. police say they have determined the shootings were a hate crime. federal prosecutors are still investigates. and the white house says it will award the medal of honor to

sergeant white who tried to save sergeants during a firefight in afghanistan in 2007. his only cover from fire was a single tree on a mountain cliff. anderson? >> incredible heroism. as you saw, the day ends in boston with a chilling reminder of what happened a year ago, the suspicious packages that were detonated. and in the year since three people lost their lives, boston strong became the rallying cry for the city. today, president obama observed a moment of silence for those who died. in a statement, the president thanked the first responders and those who showed the spirit that boston was built on in persev e perseveran perseverance, freedom and love. >> up over the clouds ♪ we long to be anywhere but here in this moment. 365 days an hour, after hate and

violence disrupted a beautiful april day. tonight, to be able to thank and embrace the first responders, will carry some of you to safety. >> the biggest lesson of all the lessons i have learned over the past year is that something in your life, in anyone's life can go horrifically, terribly wrong in a matter of seconds. yet it is up to us to make every single second count after, because believe me, they do. >> i'm glad to join in the remembrance of crystal, and martin and sean. i'm glad to share in acknowledging and supporting the families who survived, and the other survivors, many here, and some not yet ready to be here who still hurt from this tragedy and yet inspire us with their determination. >> we are boston. we are america.

we respond. we endure. we overcome. and we own the finish line. >> boston strong. that does it for us, we'll see you again at 1:01 p.m. eastern, another edition of "ac360." cnn starts now. good evening, i'll bill weir. and this is cnn tonight. it is 40 days since flight 370 vanished. four weeks since vladimir putin bloodlessly scooped crimea into russia's grip. and a year since the bombing at the boston marathon. so what have we learned about ourselves and the skies? and with conventional wisdom. and the airliner goes down, and one more example of the safety of modern air