now our nation comes together ten year after those attack to remember the heartache and horror and to honor the heroism and resilience of american spirit. this is a special edition of "good morning america." 9/11 america remembers. and the people of abc news once again right there, connecting with americans on this emotional, historic day. just as we were on this morning ten years ago. we're live from ground zero, the pentagon and shanksville, pennsylvania. now reporting, diane sawyer and george stephanopoulos. and good morning to you, i'm diane sawyer at abc news headquarters in new york with george stephanopoulos as we join to remember where we were, what we saw and the strength we found all of us together on september 11th ten years ago. t began with a blue sky, sunny morning and then game the darkest. 2,977 lost an attack that tested our nation in so many way, revealing weaknesses and strengths we haven't seen before. now we go to ground zero. it's become such a symbol of that resilience and rebirth of the united states. >> ten years later, another sky-blue day. i keep thinking the youngest of those who died, 2 1/2 years ol. you will be with us in a few moments as 20,000 family members are present at ground door row and expected to walk up for the first t me to those reflecting pools and find the names of those they love, etched around the edges. that ten years have brought us new terror threats, including the latest, george, bring us up to death. >> that's right. we have terror reports, intelligence reports that at least three people may have entered the united states, with the intent to launch a car bomb against new york or washington. p there's no reason to lessen the alert status. we honor those who lost their lives ten years ago and take the measure how fare've come. how america came back to restore and rebuild the worst attacks in history. our entire abc news is with us here in the studio in those places that were hit ten years ago on 9/11 we are taking us through the 110 year of that took us through history. there will be six occasions today when we pause together. the first two will be when the first two planes hitithe towers, one hit the pentagon next and then another outside shanksville, that's the second two and then pausing again, when the first tower fell, and then the other tower fell. >> and we're going to follow it all over the clock in the lower left-hand corner of the screen, mashing those 102 minutes as they play out on that morning ten years ago. that is the time from when the first tower was hit untnt the last tower fell. >> as we said, the families are gathering at the site of the member report yal,l, where the lives were lost, and no place has come to symbolize america's resilience, more the world trade center we building. it is, as i heard someone say, not just a scar. it is also a say credit place, and both can exist at once, and also t t power of survival, so evident there. but, now, we want to bring in our team and someone who has been your friend for so long. our friend for so long, and now, officially a member of the abc news family, and we are so glad to have katie couric here. you were in another studio that morning, watching when i was in the "good morning america" studio. >> that's right. >> and here we are together remembering. >> you know, it was such a terrifying day, and so emotional, even to revisit that day, and to listen to the two of you describe what happened. and i rewatched our coverage last night. and it was as stunning and shocking as it was ten years ago. and in fact, it was even more horrifying in hindsight, now we know what was going on in those towers, what was going on in the pentagon and aboard flight 93, united flight 93 that crashed into shanksville. today, i'll be reuniting with some of the families. i'm happy to report that many have developed a new normal and they're well into the healing process. i think it will be reassuring for everyone to see some of these family members. >> katie talked about life inside those towers. you talked to some survivors from those minute, ter tying minutes in the towers. >> really terrifying. resilience from moment one from the survivors, didn't know how to go up and down. and split second decisions made the difference between life add death. diane was talking g out be on that morning. the cruel moment, a lot of people got phone calls. i remember receiving a phone call, you got to turn on the the tv. we turned on to watch the second plane come into frame. when you see the blue sky, it takes us back to that moment. these survivors give us true hope how they lived their lives. >> christiane amanpour, you saw it through the eyes of the rest of the world. >> that's right. the whole world was river vetted. i was overseas. one thing, was the adversaries and friends of the united states, declaration of solidarity and stding, shoulder to shoulder, the famous french headline which said in french, we are all americans today, and nato invoking its charter, an attack on one is an attack on all. collective self-defense. it was an amazing moment of solidarity. we'll talk how it's changed and has come full circle. >> we also focused on families. this is the first time for many families to visit this memorial down in ground zero. it's called reflecting absence. recognizing the endurance of those who survived and courage of those who risked their lives to save others. my "good morning america" coanchor, robin roberts is at the memorial today. i can only imagine what the feel something down there. >> especially under such a blue sky, good morning, george. it's going to be an emotional day. the families were seeing the memoriri, they were sent letters where to find the loved ones names around the waterfall. president obama and mrs. obama just arrived here as well. families know they are not standing alone. they knew that yesterday as well. here in lower manhattan, a lot of local residents, they joined hands, and that human chain that they formed, was just yet another symbol of the hope and resilience that we feel here in the midst of such tragedy that happened ten years ago, george and diane. >> robin, i know the construction workers are doing the same thing. they are building not just a memorial, they are building a cathedral to hope. robin, i want to ask you, because we called it ground zweer row all these year, but i'm told the mayor has said, it's time to move on. call it something else. >> he has, diane. mayor bloomberg this week, a lot of families stand with them saying, it is time to move on and not refer to it as ground zero, but as the world trade center and september 11th national memorial and museum. the museum will be opening next september. everyone, a lot of families do not want to forget. yes, they want to remember but move forward at the same time, diane. >> robin, thanks. we look back at who we were then. small things, of course, have changed in our every day lives. not so small for the facebook users, no facebook then. victims have to rely on list serves to try to mobilize on september 10th. 24 hours of before the attack. 1% of americans 24 hours before said terrorism was even one of the nation's top problems in that age of incense. >> now it's something americans say they think about all of the time. it's something we do think about. it has been such a wounding decade in so many ways. we've also seen that resilience we've talked about. we had bill weir go back and take a look at how we've changed. it's an amazing story. >> oh, my god! >> reporter: many will ask, where were you on that severe clear morning. >> huge explosion, raining debris on all of us. >> better get out of the way. >> reporter: but here's a deeper question. >> you okay, officer? >> reporter: who were you? how did you change? is that the first time you ever stood in line to give blood or buy a flag? how long did you cheer for every passing fire truck, or flinch at the sight of a muslim scarf? did you drive cross country to help dig through the pile? and were those tears of fear or pride when your kid rushed down to enlist? and who are we now? now that the smoke has cleared? and the rubbles gone? now that the shattered stores are back in business and the president's bull horn is in a museum? and the people who knocked these buildings down will hear all of us. >> reporter: what is america after this decade of freedom fries and anthrax square, aftft tsa, ied, tei, became our new alphabet. republicans and democrats, standing together, singing together. was a blessed novelty after the florida recounts and seems even quainter after today's political standards, but arguments are the heart beat of democracy, not since the civil war have we had more to argue about. >> stop the madness. >> reporter: consider how the line between liberty and security has shoveve and shifte. . ten years ago, almost half of the country called terrorism america's most important problem. today that fear is swallowed by unemployment lines, housing prices and the next monitor storm. we can see that the always orange alert system is now history but what we canan see are the alarming numbers keeping watch from the shadows. 800,000 americans, about the population of south dakota now have a top secret security clearance. we can count the decade's toll and missing limbs from roadside bombs, harder to measure the number of families wrestling with the hidden pain of post traumatic stress. the american death toll in iraq and afghanistan is now twice as high as the number murdered on 9/11. but since less than 1% of the nation put their boots on the ground, it's all too easy to forget we've been at war longer than any time in our history. abu ghraib is long closed. guantanamo bay is still open, but in the end, the arab spring, have nothing to do with american foreign policy. so much changes in the decade. heroes of that day, rise and fade. >> conducted an operation that kaled osama bin laden. >> reporter: villains are hunted and killed and there's spontaneous joy at the scene of the crime. ♪ >> reporter: after all of those funerals, the waiting list for the new york and fire and police departments longer than ever. a new generation of the bravest, yearning to rush into the next man-made hell. there's the resiliency of a widow who managed to build a happy life after love lost, and the unity of a soldier's homecoming. that, is still who we are. that is america. "nightline" anchor bill weir on a decade passed with history and heroism. as bill was giving us that piece, president obama and president bush arriving down at ground zero, at the ground zero memorial. >> president bush, of course, in office saying, the first plane came in, he knew we were under attack. then he knew we were at war. president obama a en a 40-year-old illinois state senator. a long time ago in his life, and the life of this country. but, katie and i were talking earlier about what it was to watch this on the air, to see it unfolding. of course, all of us did that together, too, as people did call and say, are you watching? are you watching? we want to remind everyone what it was to see it as it unfolded. the incredulity as it unfolded. "good morning america" imnice to see all of you, i'm charles gibson. >> take a look at the highlights, new york city, beautiful day here. 83 -- >> we want to tell you what we know. we just got a report in that there's been some sort of explosion at the world trade center, in new york city. one report said, and we can't confirm any of this, that a plane may have hit one of the two towers at the world trade center. again, you're seeing the live pictures here. >> then there was a loud explosion, and immediately lots of screaming out on the street. >> move it, move it. come on. >> oh, no! >> world financial center, we heard a big bang, then we saw smoke coming out. >> abc's done daler, give me some description what you can see now? >> it appears there's more and more fire and smoke enveloping the very top of the building. as fire crews descending on this area, it -- it does not appear that there's any kind of an effort up there yet. remember -- oh, my god! >> that looks like a second plane -- >> that just exploded. >> we just saw another plane coming in from the side. this looks like it is some sort of a concerted effort to attack the world trade sent theory is under way. oh, this is terrifying. awful. >> to watch powerless is a horror. >> abc's peter jennings is at the anchor desk uptown and is now in position. peter, you are looking at the exact same pictures? >> we are, we will be watching this for much of the y. there's chaos in new york right now. >> let's go to claire shipman on the phone. >> that's what we're looking at right now. we know a gigantic plume of smoke coming from the executive office building. >> let me interrupt you, we have fire at the pentagon. we believe a aircraft scratched into the courtyard itself, or into that side of the building. you can hear it, let's listen. >> let's go, move! move! >> world trade center, you can see the fireman assembled here, of the police officers, fbi agents. you can see the two towers, a huge explosion now raining debris on all of us. >> better get out of the way! >> the second building that was hit by the plane just completely collapsed. the entire building just collapsed. it folded down on itself and it is not there anymore. >> the whole side has collapsed? >> the whole building has collapsed. >> the building has collapsed? >> the building has collapsed. >> let's go! let's go! >> we're talking about massive casualties at the moment, and we have -- and i'm just going to add to the chaos and trauma of the day, by saying that a large plane, has now crashed, about 10:00, in the last 15 minutes, 80 miles southeast of pittsburgh. >> they seem to have a problem at the north tower. >> let's look at the north tower, quickly, quickly coming down. >> oh, my god. both trade tower, where thousands of people work, on this day, tuesday, have now been attacked, and destroyed. >> get out of here! >> i checked in with my children, and -- who are deeply stressed, as i think young people are across the united states, and, if you're a parent, you got a kid, in some other part of the country. call them up. >> you saw it inn peter's eyes, you heard it in his voice, everyone trying to come to grips with the chaos that was spreading across the country that morning and dealing with it by reaching out. >> yes, we were somehow still in the midst of this unfolding horror, this cascade of horror, an army of generosity out around the country, as people immediately knew that this was the time to link arms and rally together. >> and rush down to ground zero where so much help was need thad day. we want to go back there, robin roberts is there. memorial going to be seen for the first time by the families called reflecting absence. robin, it is striking h h mucuc creativity and thoughtfulness has gone into producing this emmemorial. >> and it tookok lot of time, george, for that. i have to tell you, i saw it up close myself and you can see it right here. president obama and mrs. obama mr. r were there as george bush and mrs. bush were there, and their daughters were there. you see the emotion as they place their hans on the names. a lot of thought went into that, how to place and where to place, colleagues, co-workers, friend, families, officials said they honored thousands of family request. abby goldman was working on the north tower when it was hit by flight 11. abby's father was in that flight and she wanted her name placed alongside her best friend. that's one aspect of thought that went into rebuilding and remembering what happened here. a decade in the making. it's called the most complicated construction site in the world. harnessing together architectural design, a sense of loss and rebirth for the country and the victim's families. what are you hoping that they are going to experience, and feel, seeing the memorial? >> the purpose of the mememial is to give families a place to grieve, to tell the story, so that we don't forget that our grew dfreedoms are fragile. >> housed inside 16 acres of land, a museum set to open next september and two memorial pools engraved with 2,983 names of those lives loss. >> the truth of the matter, ten years to do what we've done i think is very commendable. >> reporter: the progress made since i toured the site last year with new york city mayor michael bloomberg and joseph daniel, president of the 9/11 memorial and museum is clear, trees now flourish. >> i cannot get over the changes in a year. here the survivor's tree that survived. >> the tree that survived, 95% destroyed and now flow eshing among 225 other trees. >> reporter: the two pools now flowing. >> the pools done. marking the footprint of where the north tower was. all of these people that were in the buildings that day are around this pool. to have the name, even in the rain it's almost like tears among the names themselves. it feels like we marked this sacred spot and took a lot of work, for the families and public, it's worth it. >> rain that day, but a beautiful blue sky for the families. they will get a chance, for the first time torks see it today. it will be open to the public beginning tomorrow, at 10:00 a.m. 10:00 to 8:00 p.m. they are only allowed to allow 1500 people at this point. you have to go online to reserve a ticket. you have to remember, this is still an active construction site. for the next year, year and a half, they have to limit the number of people that will have to come here and be able to see for themselves this spectacular memorial. diane, george. >> robin, the details of the memorial, just fascinating. when people go up to touch the names, it will always be at a moderate temperature, it will be cooled in the summer, heated in the winner. >> they keep it temperature controlled so it's never too hot or cold to the touch. she talked of the survivor tree. a symbol of so much. it was charged, it was broken. only 8 feet tall. it's now 30 feet tall. we remember what life affirmed. we are going to take a break, because we want to be sure, when we come back, that you are with us, as the new york city fire department, the new york city police department and the port authority, send the bagpipes into the memorial site this morning. we'll be back after a break. 1,183 fragments of steel from the trade center have been distributed to memorial sites and all 50 states and around the world. ♪ these sweehoney clustery things have fiber? fiber one. almost tastes like one of jack's cereals. uh forgot jack's cereal. [ jack ] what's for breakfast? uh, try the number one! i've never heard of that. [ wife ] it's great. it's a sweet honey cereal, you'll love it. are you guys alright? yeah. [ male announcer ] half a days worth of fiber. not that anyone has to know. fiber beyo recognition. fibeone. we're on the move. and we don't want anything, ever, to slow us down. so it's surprising that most women aren't getting enough calcium. but thankfully, with over 25 flavors, like strawberry cheesecake only yoplait original gives you 50% of the daily value of calcium and vitamin d in every cup. yoplait. it is so good. [ male announcer ] save lids to save lives with yoplait. available at your local safeway store and, welcome back, we are glad you are ginning us this sunday morning. and we want to show you again, live, ground zero, the memorial site, a morning to remember the fallen, to celebrate the resilience of a nation, as presididt obama said, chaos had come to our doorstep, but on this morning, ten years later, it is replaced, as you can see, by calm. and our abc news team is standing by at the site as well. >> that's right. we have chris cuomo down in ground zero. he's been following for ten year the heroes of 9/11, the first responders of the fire d