is it safe? with millions still stranded, airlines test the skies over europe. tonight, new questions over whether authorities were too quick to ground so many flights. under the volcano, after days of violent eruptions, the dramatic impact for those living in its shadow. the pope's promise. in an extraordinary and emotional meeting with victims of abuse, he says justice will be done. and murder mystery. we met him on this broadcast, a beloved principal who lived to make a difference. now those who knew him are asking, what went so tragically wrong? captions paid for by nbc-universal television

good evening. with most european flights grounded and passengers stranded across the globe for a fourth day, there are new questions being asked tonight about how much a danger that drifting volcanic ash cloud really poses. and whether aviation authorities may have overreacted by closing so much air space. the pushback is coming from the airlines themselves, after successful test flights today into the restricted zone. meantime, some positive developments this evening in iceland. the force of the erupting volcano itself has eased some and european air control officials say an encouraging ash forecast could allow for more flights tomorrow. nbc's tom aspell leads off our coverage tonight from london. >> reporter: a glimmer of hope today, an empty british airways 747 broke a four-day silence at london's heathrow airport to

take to the skies on a test flight to check if it's safe to start flying again. kml in london and luf tanza is germany also launched test flights. all the pilots say it's safe to fly. the airlines have been very cooperative with aviation authorities, but they are just coming out of recession and now they're losing an estimated $200 million a day. they're beginning to push back. pushing back by pressuring governments to lift the ban on flying. >> all the data from these various deferent flights that are being made are being fed into the european regulators so they can form a more accurate picture of what's happening with this ash cloud over northern europe. >> reporter: a concern some of the ash, while invisible, may still be dangerous. >> we know that volcanic ash has a very, very negative impact upon jet engines. >> reporter: today, frankfurt, berlin and warsaw allowed some flights to operate and european officials were hopeful that as many as 50% of all flights might

take off tomorrow. hundreds of thousands of passengers remain stranded at airports across europe today, hoping for one thing. >> we want to go home, back to our own country, to get home. >> reporter: today the british government told airlines to help stranded passengers by providing food and accommodation. it also announced that it's considering using the royal navy to bring home british citizens stranded abroad, including those in the united states. >> we've got to mobilize all possible transport means to get people back from the continent or from north america and elsewhere to the continent and then back to britain. >> reporter: the air travel chaos has been bad for business on both sides of the atlantic. ups and fedex have both reported cancellations and transatlantic freight shipments and several u.s. airlines have canceled tomorrow's flights to europe. and in britain, despite what are being called successful test flights, the flight ban continues at least until tomorrow evening.

tom aspell, nbc news, london. mark rosencur, who we just saw in tom's report, is a former ntsb chairman, now an nbc analyst. mark, those test flights were encouraging. depending on where this cloud goes, tomorrow could tell a different story. how will we know when it is safe to fly? >> lester, everyone is eager to get into the air. clearly the passengers, clearly the carriers themselves. but the ultimate decision is going to come from the aviation officials that are in europe and they'll be making those decisions based on the data they receive from their weather services. >> how about the pressure factor here? if i'm a passenger sitting in an airport now for the fourth day and i just watch that plane and those planes take off from europe safely, the pressure's building from that and there's the financial pressure the airlines are feeling. will that play into the decision to go? >> i don't believe so. they want to get into the air. there's no doubt about that. the aviation authorities want to put the airlines in the air, but they will not in any way, shape, or form compromise safety.

and remember, lester, it's always best to be on the ground wishing you were in the air than being in the air, wishing you were on the ground. >> well said. mark rosencur, thanks very much. the volcano that's been causing all the trouble was still erecipieupting today maki difficult for those in its shadow. chris jansing joins us once again from iceland tonight. >> reporter: residents here in iceland have the same question that travelers all around the world are still asking. how much longer is this volcano going to keep rumbling and causing troubles. today once again, scientist were in the air and on the ground looking for answers, but in truth they're getting some conflicting signals from the volcano itself. >> i have lived here all my life. >> reporter: in 42 years, he thought he'd experienced everything on the family farm until the volcano erupted ash.

his wife and three of his children evacuated while he and his team son scrambled to rescue horses, cattle, and more than 100 pregnant sheep. then today, rain turned the ash into a black spongy mud. the magnusons have been so busy taking care of the animals, they haven't had time to take care of the clean up. look at their car and this thick, black coating of ash and the bike from one of their sons left exactly where it was when they evacuated. the volcano had put on a show of ferocious intensity on saturday. dramatic explosions that created a billowing plume 30,000 feet high and blew an ominous cloud of ash over neighboring towns, turning day to tonight and getting thicker and thicker as we drove toward the volcano. we've come only about a half mile down the road, but it's gotten so dark, you can barely see, and the ash is so thick, i don't dare take off my mask. then today after so much chaos, a surprising shift that's

confounding volcanoologists. at 8:00 a.m., clouds moved in, the explosions calmed, but seismic activity increased. the question is, what does it all mean? arman and a team of volcanologists spent the day measuring hundreds of measurements on the degree. >> we can compare the physical data that we have already and by that, we can start to get anning educated guess. >> reporter: as experts evaluate whether it's like to again show its massive power, the rumblings inside raise a bigger concern, that they could trigger the nearby much-bigger volcano, katla. >> every single volcanologist

believe it's likely that katla will below and it has the potential to be 100 more times than this one. >> not making it any easier to get a clear picture this evening. the volcano even interrupted president obama's travel plans. he and other world leaders had to cancel plans to attend the state funeral of poland's president today because it was considered too risky to fly. the funeral went on in krakow with them and nbc's jim maceda was there. >> reporter: a week of mourning came down to this. a funeral service. the flag-draped coffins of presidents lech kaczynski and his wife, maria, were blessed during a high mass in the ancient capital of krakow. dignitaries packed the small church, mostly from central and eastern europe, they came by car or train. but others sent their regrets. presidents barack obama and nicolas sarkozy and german

chancellor angela merkel among dozens unable to fly through the cloud of ash hanging over europe. one exception, russian president dmitry medvedev. kaczynski was a divisive figure often alienating allies, but today all poles, it seemed, were united in grief over the loss of their president. the tens of thousands loined the streets and as the coffins moved through the old town, some applauded. others chants, thank you lech and maria kaczynski. even critics were moved. >> president kaczynski wasn't a very important person to me, but i think this is a very important historical moment. >> reporter: capped by the burial inside a crypt reserved for kings and heroes, the kaczynskis, once the nation's first couple, had become symbols of its worst tragedy since world war ii.

jim maceda, nbc news, krakow. there was a dramatic and emotional development today in the ongoing crisis facing the catholic church over allegations of child abuse by priests. the pope, who has faced questions about his own handling of the crisis, today met with victims of abuse and promised them justice would be done. here's nbc's ron allen. >> reporter: the pope's visit to malta brought him to a largely catholic nation, struggling with allegations of priests abusing young men and boys. in a private meeting, the pope confronted those emotional charges face to face. >> promise you're going to pray for me. he told me, i'm grateful to you, you have the courage to show your face. it was emotional. >> reporter: lawrence says the pope had tears in his eyes as he listened to his story of being molested repeatedly as a child by priests at an orphanage. he was one of eight men the pope met and prayed with. a vatican statement said the pope was deeply moved by their stories and expressed his shame

and sorrow over what victims and their families have suffered. grets says meeting the pope restored his lost faith. >> this is an experience that's going to change my life. you know, now i can -- i believe, you know. >> pope benedict has met with victims on at least two other occasions. in australia and here in the u.s., but that was before new allegations this year that the church covered up or did nothing about known cases of abuse. >> no one, you know, unless their heart is of stone, can listen to these stories and not be moved. >> reporter: father thomas reese suggested the pope listen to more stories, everywhere he goes. >> the church has to continue to condemn the abuse and apologize, apologize, apologize. >> reporter: the vatican also says the pope gave assurances the church is doing all it can to bring to justice those responsible for abuse. there were no specifics.

>> and i tell, i say, listen, i don't want to make damage to the pope. i am doing this for awareness, you know? he told me, i'm proud of you, the pope. >> reporter: and as more allegations have come to light, many of the faithful think the pope must address the crisis more directly and for all to hear. ron allen, nbc news, new york. we have an update now on the bombshell late last week that the securities and exchange commission had filed fraud charges against high-flying wall street firm goldman sachs. many critics have faulted the s.e.c. for not doing enough to head off a financial crisis. but cnbc's trish regan tells us tonight that the agency is now taking the gloves off. trish, good evening. >> hi, good evening, lester. well, this is an agency that is a very different agency, perhaps, than the one we have seen in the past. that is the message tonight. a stronger, more aggressive securities and exchange commission. in the agency's first public

statement since that news about goldman sachs broke on friday, the s.e.c. enforcement director, robert cue sammy tells us, and i quote, we have brought and will continue to pursue cases involving the products and practices related to the financial crisis. now, lester, the language here that's most critical is "continue to pursue." officials tell me that pursuing financial fraud is a top priority right now at the s.e.c. and that they have a wide range of cases that they are currently looking into. they also point out that they are better equipped to handle some of these investigations because there has been a restructuring within the s.e.c. so that there are now specific groups that are targeting specific kinds of fraud. so, really, the bottom line tonight, lester, from the s.e.c. to wall street, watch out. >> trish regan with that late update. thank you. when "nightly news" continues, a look at what iceland's volcano may be doing to the air we breathe. and up next, we met him here on this broadcast. a man making a difference for some d.c. school kids.

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if you cannot afford your medication, call 1-866-4-trilipix for more information. trilipix. there's more to cholesterol. get the picture. has stunned washington. the victim -- a man we met here on this broadcast last year. educator brian betts was known for making a difference in the lives of his students. now his life has come to a tragic end and investigators are trying to figure out why. nbc's norah o'donnell reports. >> all right, folks! 8:35. let's start to move in, please! >> reporter: he was a principal who changed children's lives. >> and i'm very, very proud of you. >> reporter: 42-year-old brian betts, once a phys ed teacher, was hand picked two years ago by d.c. public schools chief, michelle rhee, for what seemed

like an impossible mission. the goal to transform the underperforming shaw middle school, all part of an overhaul of d.c. public schools. principal betts' message to kids was simple -- as he told tom brokaw last year. >> if you come to this school and do what it is we're instructing you to do, you can pick whatever path you want in this life. and as you're doing that, be nice to each other. >> reporter: betts' love and respect for his students was mutual. >> i used to get into a lot of fights and being very negative. >> reporter: so what changed? >> when changed that? >> mr. betts. mr. betts. i can say mr. betts, he's a very positive person and he has a good attitude and being around people with positive attitudes, it helps bring up your spirit. >> reporter: here where betts taught, his students are devastated and mourning the loss of their beloved principal. >> i don't know why anybody would want to kill him or harm him in any way. he was a good person. he was a good man. >> a senseless tragedy that is

just -- tremendous loss. >> reporter: betts was found murdered inside his silver spring maryland home on thursday night, shot to death. >> there was no sign of forced entry into the house. >> reporter: that's why police don't believe it's a random killing. his suv was found yesterday in d.c., 14 miles from his maryland home. a murder mystery that has now left a community without its hero. >> he believed in every kid that walked through the door. he really treated each one like they were the most important kid in the world and they felt it from him. >> reporter: and now brian betts' intense devotion to his students will be his legacy. norah o'donnell, nbc news, washington. when "nbc nightly news" continues, more fallout from that volcano. is it making the air unsafe to breathe? tonight, questioning the side effects on planet earth. you don't need a rematch-- but a re-think-- with lunesta. lunesta is different. it keys into receptors that support sleep,

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story. there's been a lot of attention paid to the effect iceland's volcano is having on air travel,

but what about the environmental impact? what is all that gas and ash doing to planet earth? as we kick off green week, tonight, some answers from our chief environmental affairs correspondent, anne thompson. >> reporter: volcanic ash turns day into night in iceland. it's 3:00 in the afternoon on saturday and this reporter describes what she cannot see. the dust storms created by the volcano are ominous to look at and drive through. carrying gases that could potentially harm the environment. one such gas is flourn, a highly corrosive chemical that could poison animals. local farmers round up their livestock to keep them from eating ash-covered grass. >> they put it in tooth paste to help with tooth decay in parts per million. >> reporter: another lurking hazard -- silica. a basic building block of

volcanic rocks. in fine particles, it can be dangerous to people. >> it gets into a part of your lung where it can kind of stick and your lungs have trouble getting it out. >> reporter: the world's health organization urges residents in areas impacted by the ash cloud to listen to their local health officials. it cause if people go outside and experience nose and throat irritation, they can return indoors and limit their outdoor activities. this third potential problem includes sulfur dioxide spewed from the volcano. but its reflexive properties can also cause global cooling. could it actually help reverse global warming fueled by man-made carbon dioxide, co2. >> it's hard to reverse that without reducing these greenhouse gases like co2. >> reporter: compared to air travel, the volcano's impact on the environment so far is minimal, but if this volcano erupts for several months or even years, scientist say the

damage could become significant. anne thompson, nbc news, new york. up next here tonight, looking out for kids others have given up on. a guardian angel who is making a difference. everything changed. mom. ♪ i didn't know what to do. that's when i asked my doctor about exelon patch. he said it releases medicine continuously for 24 hours. he said it could help with her cognition, which includes things like memory, reasoning, communicating and understanding. [ female announcer ] the most common side effects of exelon patch are nausea, vomiting and diarrhea. the likelihood and severity of these side effects may increase as the dose increases. patients may experience loss of appetite or weight. patients who weigh less than 110 pounds may experience more side effects. people at risk for stomach ulcers or who take certain other medicine should talk to their doctor because serious stomach problems, such as bleeding, may worsen. [ woman ] mom's diagnosis was hard to hear, but there's something i can do.

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lifelong before the recession, recovery in some neighborhoods is measured one life at a time. from detroit, "dateline nbc's" chris hansen shows us how one woman's personal rescue mission is making a difference for children left alone. >> god, i just thank you for being my father today. >> reporter: on a saturday morning on one of detroit's countless vacant lots, cordette joins a weekly prayer group. >> i thank you for blessing me to be a mother today. >> reporter: cordette has made it her mission to rescue children abandoned by their parents. >> hey, you guys, come here a momentum. >> this is the baby boy. >> reporter: she knows the odds are against these boys and the baby girls she's raising. 25 years ago, she took in andre, who she says was abandoned by his crack-addicted mother.

she struggled to keep him out of trouble, but he found his share of it anyway. >> the streets swallowed him up real fast. >> reporter: andre dropped out of school, became a teen father, and landed in jail. she wants better for her younger ones. >> give me five. >> reporter: deante, who's in fifth grade, started the school year reading at only a second-year level. cordette insisted he get tutoring and he's already improving. she's also the president of the parent organization at deante's school. the principal says cordette understands both worlds -- the streets and the system. >> she can go inside the community, which many of us can't do that. and she can come out and come out swinging. and she demands respect. >> excuse me, sweetheart. can i talk to you for a minute? you had a fight with somebody? >> yes. >> okay. but is it worth you going to jail? >> no. >> reporter: when she sees trouble brewing outside the

school, like this young man with a stick, apparently looking to settle a score, she steps in. >> so just calm down so you don't get in trouble, okay? because it ain't worth all that. >> reporter: lately, she's been in court, seeking guardianship of the younger ones. for torian, it's now official. >> i am full guardian over him. i am his mother now. >> she's a fighter and she's teaching her children to be fighters as well. >> reporter: you've taken in six. >> mm-hmm. >> reporter: are you done? >> no. i don't feel that i'm done. i feel some more is coming. >> reporter: setting an example for her city and for all of us. chris hansen, nbc news, detroit. >> much more from detroit in a special dateline, "america now: city of heartbreak and hope" coming up at 7:00, 6:00 central. that's "nightly news" for this sunday. brian williams will be here tomorrow. i'm lester holt reporting from new york. for all of us here at nbc news, good night.