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As the World Trade Center in New York City burns after being hit by two hijacked aircraft, another hijacked aircraft is deliberately flown into The Pentagon, killing all 64 people on board and 125 on the ground.
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00:02The Pentagon has served for more than 60 years as a symbol of power in defense of freedom.
00:07A five-sided fortress to safeguard the American dream.
00:12Then on September 11, 2001, terrorists tested its strength.
00:17They turned a commercial jet into a weapon of destruction.
00:24The United States suffered a tragic loss of life that day.
00:28But America's fortress proved to be a shield, protecting the lives of thousands of people who worked there.
00:36Now, with cutting-edge computer graphics, we reveal exactly what happened.
00:42Disasters don't just occur, they're a chain of critical events.
00:49Unravel the fateful decisions in those final seconds from disaster.
00:58The United States of America.
01:01Arlington, Virginia.
01:03The Pentagon.
01:05September 11, 2001.
01:096.46am. Daybreak.
01:13While many Americans are asleep, the citadel of American defense kicks into action.
01:19WTW time, this is the 11th of September. Good morning, Armature Day.
01:24Army Lieutenant Colonel Marilyn Wills is already planning her day.
01:28That morning, I called the girlfriend and asked if she could get the girls to school, because I had to
01:32go and my husband had to go.
01:33So I kissed them, smacked them. I'm out.
01:37Marilyn is one of almost 23,000 employees who converge on the Pentagon every working day.
01:45Men and women.
01:47Civilians. Soldiers and sailors.
01:50Marines and Airmen.
01:54The Pentagon is one of the largest office buildings in the world.
01:59Its five floors are made up of a unique five ring design.
02:03Almost 30 kilometers of corridors weave through more than 600,000 square meters of office space.
02:09The equivalent of three Empire State buildings.
02:14It's a city unto itself, with all conveniences under one roof.
02:19And a high-tech operation center, monitoring the building's safety and security.
02:277am.
02:28Bobby Hogue, a top Marine Corps lawyer, arrives at the Pentagon.
02:32I had a standing breakfast meeting with the assistant commandant of Marine Corps.
02:35We met at the general officer's mess.
02:38You know, oh, dark 30, as the Marines say.
02:42The day also begins early for those catching West Coast flights out of Washington Dulles International Airport.
02:547.18am.
02:56Terrorists carrying knives and box cutters make it through the airport security checkpoint.
03:02And board American Airlines flight 77.
03:098am.
03:11The Pentagon offices are now in full swing.
03:16Marilyn Wills is about to set off for her departmental meeting.
03:20Her military career spans 20 years.
03:23For the last two, she served as army personnel and congressional affairs officer.
03:298.20am.
03:30My office mate and I discussed what I'm going to talk about at the Tuesday meeting.
03:36And so I told her, see you later.
03:38And I went on to the conference room.
03:408.20am.
03:428.20am.
03:42Air traffic control is at Dulles Airport.
03:44Clear American Airlines flight 77 for takeoff.
03:47American 77, your departure frequency will be 125.05.
03:51Runway 30, cleared for takeoff.
03:53125.05.
03:54Runway 30, cleared for takeoff.
03:56American 77.
03:57On board of 53 passengers, two pilots, four flight attendants and five men planning mass murder.
04:04Among the passengers are a family of four, a political commentator and three students with their teachers who are on
04:09an educational trip led by two employees of the National Geographic Society.
04:14The aircraft's fuel tanks carry enough for its 4,220-kilometer cross-country flight to Los Angeles.
04:238.46am.
04:24This just in, you were looking at obviously a very disturbing live shot there.
04:29That is the World Trade Center and we have unconfirmed report that a plane has crashed into one of the
04:34towers of the World Trade Center.
04:37An eerie stillness descends over the Pentagon's offices.
04:45Nearly everyone is transfixed by the events in New York.
04:50John Yates is a security manager at the Pentagon.
04:54So I stood there for about four or five minutes watching and walked back to my desk, called my wife.
05:00Before she ended up, she said, Honey, do me a favor and work from underneath your desk for the rest
05:05of the day.
05:06And so I laughed and I said, Sure, I will.
05:09I said, I love you and I'll see you tonight.
05:11At this moment, no one is quite sure of the gravity of the situation.
05:198.50am.
05:2130 minutes into its journey, American Airlines Flight 77.
05:26It's now at its cruising altitude of 10 and a half thousand meters and is crossing the Ohio-Kentucky border.
05:32The air traffic controller at the Indianapolis Control Center radios the pilot.
05:37American 77, you're a direct bomber.
05:40Direct bomber from American 77, thank you.
05:44Those are the last words heard from the pilot.
05:49American 77, American Indy radio check, how do you read?
05:56American 77, American Indy radio check, how do you read?
06:00There's no answer.
06:01The air traffic controllers become concerned.
06:05You guys never been able to raise him at all?
06:08No, no, no radio communications and no radar.
06:12In the same instant, the plane's flight information disappears from the controller's radar screen.
06:17They no longer know where the plane is.
06:218.54am.
06:23Without anyone realizing, American Airlines Flight 77 has changed course.
06:28It turns around and is heading back east.
06:32On the third floor of the Pentagon, Bobby Hogue, Peter Murphy and another Marine Corps lawyer discuss a case.
06:419.03am.
06:46A second plane hits the World Trade Center.
06:51Bobby Hogue is convinced this is a terrorist attack.
06:55So, everybody knows now what's happening.
06:59And, you know, now you have to act.
07:02You have to do something.
07:03I mean, we're in the Pentagon, it's the national military headquarters.
07:06So, I start asking our clerk, you know, call the security guys.
07:12Find out what the status of the building is.
07:13Everybody's watching TV.
07:14Nobody's watching the building.
07:15What's going on?
07:16And the corporal came back to me and said, you know, threat conditions normal.
07:21I said, well, that can't be right.
07:23But within seconds, the security level of the building increases rapidly.
07:28In offices throughout the Pentagon, tension mounts.
07:33Lieutenant Kevin Schafer watches the breaking news on TV from his office on the ground floor.
07:38I couldn't concentrate on my work.
07:40And I stood up at my desk and I just remember just standing there and watching the events unfold.
07:46Some of my colleagues were intending to call their wives or their spouses.
07:52You know, it was an emotional moment where they wanted to reach out.
07:55The Pentagon is now a target as the national crisis comes closer to home.
08:01Firefighter Alan Wallace is one of a three-man crew based at the Pentagon's fire station.
08:07He's busy checking the Pentagon's fire truck.
08:10At noon today, President Bush is scheduled to arrive.
08:149.30 a.m.
08:16Alan received a call from his fire chief.
08:20The information that Campbell gave me is that the government is considering this a terrorist attack.
08:24There's no doubt about it.
08:26And something like this could very possibly happen in Washington, D.C.
08:29And if that did happen, then our fire truck would be responding to that incident more than likely.
08:35Marilyn Wills is still in her meeting, isolated in the conference room on the first floor.
08:40She knows nothing about the terrorist attacks on the Twin Towers.
08:43And I just happened to glance at my watch and say, boy, this meeting is going a little long.
08:509.32 a.m.
08:52American Airlines has grounded all planes nationwide.
08:56As Washington-Dulles controllers clear the skies, they spot a fast-moving blip on their radar.
09:01It was an unidentified plane to the southwest of Dulles, moving at a very high rate of speed.
09:08I had literally a blip and nothing more.
09:13Traveling at 750 kilometers an hour, the plane is heading straight for the protected airspace covering the Capitol and the
09:20White House.
09:21And it was just a countdown.
09:23Ten miles west.
09:25Nine miles west.
09:27And all of a sudden, the plane turned away.
09:32But the unidentified plane makes a dramatic 330-degree turn, nearly a complete circle.
09:38It's now heading directly for the Pentagon.
09:42We lost radar contact with that aircraft.
09:45And we waited.
09:47And we waited.
09:48And your heart's just beating out of your chest.
09:58September 11, 2001.
10:01Two airliners slam into the Twin Towers in New York City.
10:109.32 a.m.
10:12Another aircraft has dropped off the radar and is heading straight for the Pentagon.
10:18At 9.37, firefighter Alan Wallace is outside the Pentagon's west wall by his firetruck.
10:24We passed the right front corner of the firetruck and probably 15 feet further than that.
10:31And I happened to look up and look to my left and there is an airplane.
10:369.38.
10:39The Boeing 757, now at 850 kilometers per hour, is one second from impact.
10:45It flies so low, it knocks down three streetlights and slams into the Pentagon's west side.
10:53A security camera captures the immediate aftermath.
10:56This is the only photographic evidence that exists of the impact.
10:59The plane tears through the west wall.
11:02Kevin Schafer's office on the ground floor takes a direct hit.
11:05I just remember a gigantic fireball, the space exploding and knocking me to the ground.
11:11I was on fire and I knew I had to extinguish the flames.
11:16But it just happened so quickly and truly, literally, the shock of the moment really disoriented me.
11:24John Yates and Marilyn Wills are on the first floor, immediately above the impact zone.
11:32Everything I touched, burned me.
11:35Everything was instantaneously hot, just like the inside of an oven.
11:38And I could feel water on my back from the sprinklers.
11:41Someone grabbed the back of my pants and I told her, hold on to me.
11:46Don't let me go wherever I go.
11:48I got you. We're going to get out of here.
11:51So we started to crawl.
11:52I was first and then the civilian was behind me.
11:56Not knowing there were several people behind her.
11:59Because you couldn't see anyone.
12:01If you put your hand in front of your face, you could not see your hand.
12:04It was that dark with smoke.
12:08And the lady behind me tugged on my pants and said she couldn't go any further.
12:12Because the smoke was just so intense.
12:14And she's like, every time I breathe, it hurts.
12:17And so I had on my Black Army sweater.
12:20And whatever was falling from the ceiling, liquid, I was putting my sweater in it and sucking on it.
12:27Because my mouth just felt like it was on fire.
12:30And so I passed it to her and I said, just suck on this.
12:33And I said, don't swallow, just suck on it and spit it out.
12:39Operators in the building's Defense Protection Service Communication Center receive frantic phone calls from trapped employees.
12:47They coordinate the rescue effort and stay at their desks, even while the entire building is being evacuated.
12:56On the third floor, seven and a half meters above the plane's impact, Bobby Hogue is thrown across his office.
13:03Thick black smoke turns day into night.
13:07Bobby and four co-workers fight to breathe, desperately searching for a way out.
13:13But there's a problem with the escape route.
13:16To the south of us, the floor is obviously broken open and that doesn't look stable.
13:20We were afraid and we were in a tight spot.
13:26Firefighter Wallace dives for cover.
13:28He suffers only minor cuts and burns.
13:31The blast sets his fire truck ablaze.
13:34But without a moment's hesitation, he climbs into the burning vehicle to call for backup.
13:40Formrider rescue engine 161, you're responding.
13:44Need for box 7560, you're reporting an airliner into the Pentagon, heliport side.
13:499.40am.
13:54The roads around the Pentagon come to a standstill.
13:57Rescue teams have to force their way through to reach the disaster area.
14:03Thick black smoke is choking Kevin Schaefer.
14:07But as he crawls over piles of hot debris and intense fires, he spots a possible escape route.
14:12I could see the sunshine almost, but it was all obscured by the smoke.
14:17I really just started racing towards that light.
14:20And I walked through this hole.
14:23And it was obviously this freshly blown out hole.
14:31But up on the first floor, Marilyn Wills is still trapped.
14:35We just started banging on this windowsill, just with feet and hands and the heel of our hands.
14:41And the windowsill popped open.
14:43The lady who was behind me was a lot older than we were, so we knew she had to go
14:48first.
14:48And the soldier who was standing there had been burned severely.
14:52So we lowered him down.
14:54So at that point it left my boss and I in the window.
14:59And I knew my office mate was still in there because she didn't have a meeting.
15:03And I knew several other people had to be in that area.
15:06And so he told me it was my turn to go.
15:09And I told him I couldn't because I wanted to go back.
15:14He pretty much gave me an order and said, you go out of the window now.
15:20I think that was the hardest thing I had to do because I knew people were in there.
15:26But I knew it was suicidal if we went back.
15:30So I got out of the window.
15:359.45 a.m.
15:38Ten fire trucks battle to gain control of the blazing inferno.
15:42Temporary triage units treat those victims that do escape.
15:46By the blazing west wall, Alan Wallace helps those trying to get out through windows above.
15:52The building is on fire.
15:53These people coming out of the building are terrified.
15:55They're hurt and they're burned. They don't know where they are.
15:57The fire is coming out of the top half of the window and the smoke is blowing out of the
16:00bottom half.
16:01And these people are trying to get out of the building.
16:03As the inferno rages, it's impossible for firefighters to reach those trapped on the third floor.
16:10Black smoke billows from both ends of the corridor.
16:14Bobby Hogue and his four co-workers keep searching for a way out and come across the crack in the
16:19floor again.
16:20Now it's opened up and it's dropped even further.
16:24And you can see the fire coming up through the floor.
16:28They're trapped. The odds are against them.
16:32Follow my voice. Come, come this way.
16:35Some young guy saying, there's a way out here. There's a way out this way, this way.
16:39So we don't question much. We just kind of grab onto each other and hunch over and make for the
16:43door.
16:469.55 a.m.
16:5017 minutes after the plane plowed into the Pentagon, firefighters hear the building creaking and cracking.
16:56Huge slabs of the floor are sinking.
16:59It's about to collapse, so they rush to evacuate the area.
17:049.57 a.m.
17:1019 minutes after impact, a 23-metre section of the building collapses.
17:17It's an agonizing 10 minutes before firefighters get the all clear to resume rescue efforts.
17:26Amazingly, Kevin Schaefer, Marilyn Wills, John Yates and Bobby Hogue all manage to make it out in time.
17:33They and other survivors are rushed into emergency helicopters and ambulances.
17:3711.30.
17:40The fire is now so fierce that it takes firefighters almost 24 hours before they can extinguish the last of
17:46the flames.
17:47For the first time in American history, terrorists attacked the premier defense headquarters of the most powerful nation in the
17:54world.
17:58Now, by rewinding the events of that day, and by going deep into the investigation, we can reveal what happened.
18:12Cutting-edge computer graphics will take you where no camera can go, into the heart of the disaster zone.
18:19This terrorist act has cost the lives of 184 innocent victims, 59 passengers and crew aboard the plane, and 125
18:27Pentagon workers.
18:29Almost 23,000 people work in the Pentagon every day.
18:33When the plane rams into the building at 850 kilometers an hour, it's loaded with 20,000 liters of jet
18:40fuel.
18:41It's an explosive force with the energy of almost 500 kilograms of TNT.
18:47Much more of the building should have been destroyed.
18:50If investigators can figure out how so much of the Pentagon survived, they can protect more people in offices across
18:57America and the world.
18:59The Federal Bureau of Investigation takes over the crime scene.
19:03And the American Society of Civil Engineers gather a team of six fire and structural experts to examine the building's
19:10damage.
19:11But investigators don't start with the building.
19:14First, they need to concentrate on the flight and examine how the plane entered the Pentagon.
19:20They begin by listening to air traffic flight recordings.
19:2478 minutes before impact, American Airlines Flight 77 gets clearance for takeoff from Dulles International Airport.
19:31American 77, your departure frequency will be 125.05, runway 30, cleared for takeoff.
19:3812505, runway 30, cleared for takeoff.
19:52Data from the aircraft's black box proves that American Airlines Flight 77 begins a 180 degree turn and heads back
19:59east over West Virginia.
20:0342 minutes before impact, all contact with the flight is lost.
20:08American 77, American Indy radio check, how do you read?
20:12What was happening in that aircraft after the pilot's last communication with air traffic control?
20:17Radio check, how do you read?
20:18As a former air crash investigator with the National Transportation Safety Board, Bob Francis has a good idea.
20:25Clearly there was no problem at 8.50.
20:308.56, hijackers in control of the airplane.
20:35One of the very first things the hijackers would have done would have been to turn the transponder off.
20:44The transponder is a device that relays the aircraft's flight details, its number, speed and altitude, to air traffic control.
20:53With the transponder off, American Airlines Flight 77 is reduced to a small blip on the radar screen.
21:01They no longer knew which aircraft on their radar was American 77.
21:07They basically lost this airplane.
21:10It means that for 36 minutes, American Airlines Flight 77 is able to fly east towards Washington, D.C.'s protected
21:17airspace, undetected by air traffic controllers.
21:22The difficulty was that they were looking west, because that was the direction that the aircraft had been going in,
21:29and they assumed that was the way that it was continuing to go.
21:34Six minutes to impact.
21:36Suddenly, Washington air traffic controller Danielle O'Brien sees the fast-moving blip headed for the White House.
21:43But before she can react, it disappears.
21:47Four minutes to impact, the black box confirms that the plane has entered a dive.
21:53Dropping 670 meters, turning 330 degrees to line up with the Pentagon, it increases its speed to 850 kilometers an
22:01hour.
22:07American Airlines Flight 77 slams into the Pentagon's west wall.
22:14This computer recreation shows that the plane is flying dangerously low.
22:20Now, the angle at which it hits the building becomes the new focus for investigators.
22:30Five terrorists have hijacked an American Airlines jet and crashed it into the ground floor of the Pentagon.
22:42Using advanced computer graphics, we go into the heart of the disaster zone to reveal exactly what happened.
22:49Discovering how the plane hit the building is a critical first step in investigating the tragedy.
22:56There are no images of the actual impact.
22:59The only photographic evidence is from a security camera.
23:03It takes one photo every second.
23:05But at 850 kilometers an hour, the plane hits the building between photos.
23:12The one shot that would help the investigators, the critical moment of impact is missing.
23:19Lead structural engineer, Alan Kilshimer, is one of the first experts on the scene.
23:23When I first got there, I had no idea how the plane hit the building.
23:27Alan focuses on the plane's entry point.
23:32You could see the marks on the limestone where the right wing had made a mark as it went in.
23:37So you knew it was banked with the right wing higher and the left wing lower.
23:43938.
23:45The plane comes in at an angle.
23:47The right wing hits the sturdy cement and steel base of the first floor slab and breaks off.
23:53But what happens to the left wing?
23:57Investigators make another discovery.
23:59Just in front of the left side of the hole, they find pieces of an aircraft wing buried nearly half
24:05a meter into the earth.
24:08Investigators now know exactly how the plane hit the Pentagon.
24:12The plane approaches the west wall diagonally, flying nearly level with the ground.
24:18Until, 0.1 of a second before impact, the plane rolls slightly to the left.
24:24At the moment of impact, the lower left wing and engine strike the ground at nearly the same instant that
24:29the nose hits the building.
24:33It's a critical piece of information because the angle at which it enters the building dictates the path the plane
24:39follows inside.
24:45There's a thin line between surviving or not, and it's a matter of centimeters.
24:53Now investigators want to know what happens as the plane plows through the building.
25:00For clues, they turn to dramatic footage of a controlled aircraft crash test.
25:07In 1984, the Federal Aviation Administration tested the effectiveness of a fire-retardant fuel by crashing a Boeing 720 aircraft
25:15in the Mojave Desert.
25:19They match this experiment to what happens to Flight 77.
25:25First, they compare the speeds.
25:28The plane in the experiment was traveling at 274 kilometers an hour when it hit the tarmac.
25:36From its black box, investigators know the hijacked 757 was flying three times that speed when it hit the Pentagon,
25:43850 kilometers an hour.
25:46Then they compare the distances each plane traveled after crashing.
25:51The test crash Boeing 720 slid nearly 370 meters before it stopped.
25:59But the conditions of Flight 77 were not the same.
26:03It was traveling three times faster into a fortified building.
26:08Pentagon investigators find the furthest remnants of the plane only as far as 95 meters into the building.
26:15What investigators now want to know is how exactly did the building structure slow down the plane so much that
26:22it limited damage.
26:26Destruction to the ground floor is all they have to go on.
26:31In a new age of terror, structural experts need to find out how to protect people in office buildings against
26:37a terrorist attack.
26:40The plane crashed into the Pentagon with such force it wiped out many of the supporting concrete columns.
26:4520 meters in.
26:4830 meters in.
26:50But then, at almost 50 meters inside the building, columns are damaged but still standing.
26:58Investigators are able to build a clear picture of what went on inside the Pentagon.
27:02So what really happened was that the entire plane disintegrated as it went through the building.
27:08This is the moment of impact.
27:10The aircraft's nose acts like a bullet, tearing an opening into the building's face.
27:17One hundredth of a second after impact, the plane hits the first eight columns and begins to break up.
27:24Two hundredths of a second.
27:26There's still momentum and what's left of the plane continues traveling forward through offices.
27:32Half a second.
27:33The black box cockpit recorder and the landing gear punch nearly 100 meters into the building.
27:38These are the only recognizable parts of the plane to survive.
27:51Within the offices that I worked in, there were 24 people who died that day.
27:56Three people in my immediate office, my boss and two of my coworkers.
28:00And then 21 other of my friends.
28:05The plane tears through the ground floor offices just below John Yates and his colleagues.
28:11But it's fire and toxic smoke that claims the lives of nearly two-thirds of the victims.
28:18Fire protection engineer Tom Stanton evaluated the performance of the building.
28:23What these forces did was push everything all around through the building into piles.
28:28And they burned, taking out the walls, taking out the ceilings, everything and just pushing it everywhere.
28:34These piles are like massive bonfires.
28:38All they need now is fuel and ignition.
28:43At impact, the aircraft is carrying 20,000 liters of fuel.
28:48Some of the fuel feeds the huge 127-meter-high fireball outside.
28:53But the rest comes into the building with the plane, moving almost 240 meters per second.
28:59It sprays jet fuel everywhere, including onto the piles of debris.
29:05John Yates is on the first floor.
29:10My glasses were still on my head.
29:13And when I took them off, I thought they were covered in blood.
29:17Because there was something on them and I now know that it was jet-fueled.
29:20Stan Ames is a fire scientist who studies how fire behaves.
29:24Let's imagine what it would have been like inside that building.
29:28Suddenly and explosively filled with a fine mist of aviation fuel, followed by fire that burnt it explosively.
29:35Within an instant, it changed from fresh air to intense heat.
29:40This type of fuel-air reaction is used in bombs that are designed to explode,
29:46remove all the oxygen from the atmosphere and produce lethal conditions.
29:50Pentagon workers who survived the initial impact now face an unbearable set of circumstances.
29:56You swallow, you could feel your lungs expanding and shrinking,
29:59and you couldn't use your eyes because the smoke was so intense.
30:11Conditions are intolerable.
30:13Fires and explosions rage along the plane's 95-meter track through the building.
30:18As widespread as those fires were, some people, like John Yates, did survive.
30:23But how?
30:26Just one year before 9-11, the Pentagon's fire protection systems were overhauled.
30:32Engineers installed high-powered sprinklers that could handle twice the amount of fire.
30:38As luck would have it, these new sprinklers existed in the very part of the building the plane hit.
30:43John Yates, on the first floor, suffered second- and third-degree burns over 35% of his body.
30:49But without these extra sprinklers, he wouldn't have survived.
30:53Sprinklers are the most important thing when it comes to fire suppression or fire protection,
30:58because they're automatic, they're very reliable, and they do the job and they do it well.
31:04But it was a different story on the ground floor.
31:07Here, investigators were sure no one in the plane's path could have survived.
31:12But remarkably, one man did.
31:15How he got out alive is an incredible story.
31:23Fires rage in the west wing of the Pentagon after terrorists crash American Airlines Flight 77 into the ground floor.
31:38There we were, in the heart of the Pentagon, and all of a sudden, in an instant, everything is exploding
31:44around me.
31:46Dr. Georgine Glatz is chief engineer of the Pentagon renovation program.
31:51You see all the damage, and you don't have a clue who behind those walls and desks survived.
32:01For answers, the Pentagon task force turns to those who did make it out alive.
32:06They plot their exact positions within the critical zone and listen to each gruesome story.
32:13Six weeks into the investigation, Dr. Glatz has interviewed 30 survivors.
32:18Then she hears of a man still recovering at Washington Hospital Burn Center.
32:23His name is Kevin Schaefer.
32:25Her interview with Kevin reveals something remarkable.
32:30Kevin's desk was in the direct path of the plane on the ground floor.
32:35I just remember a gigantic fireball, the space exploding, and knocking me to the ground.
32:43The forces of the plane, moving at almost 240 meters per second, drags fuel into the building, drenching stacks of
32:50debris, which ignite.
32:53How did Kevin survive?
32:57I took off in another direction and just literally started crawling and climbing over debris and through and around pockets
33:06of quite a bit of fire.
33:11As the plane comes into the building, it acts now like a big tank round.
33:15It's almost like if you're blowing up something in a rock quarry and you have milliseconds apart different explosions.
33:21That's what was happening.
33:24This film shows what happens during an explosion.
33:29The first stage is the bomb's lightning-fast blast wave.
33:35As energy pushes out from the explosion, it compresses air particles in its path to create a shockwave.
33:42It travels faster than the speed of sound, demolishing everything in its path.
33:49Using advanced computer graphics, we see in those milliseconds after impact how the blast wave moves through the Pentagon's ground
33:56floor.
33:59As the plane plows through the building, there are multiple explosions, spaced milliseconds apart, creating shockwaves that follow a path
34:09of least resistance, bouncing off solid objects, moving in chaotic paths throughout the building.
34:18The ricocheting blast waves just missed Kevin.
34:21If he'd been standing just centimeters to his left or right, he would have been hit squarely by the blast
34:27waves.
34:28Had I been knocked unconscious, I don't think I would have survived in that space. I mean, I clearly wouldn't
34:32have.
34:34The blast waves that missed Kevin blow a hole into a roadway.
34:39This provided his only means of escape.
34:43Kevin got out by crawling another 28 meters.
34:47He suffered burns over 42% of his body and had two cardiac arrests while in hospital.
34:54How the blast waves that missed Kevin behaved has to do with the Pentagon's unique design.
34:59The Pentagon consists of five rings.
35:03The roadway that separates B and C rings is called A and E Drive.
35:09The shockwaves raging through the ground floor are enclosed within three rings of offices.
35:14There was no way for the pressure from all these explosions to relieve itself.
35:18And the first time it could relieve itself is when it hit A and E Drive.
35:29In the end, the path of destruction is only a small sliver of the entire 600,000 square meters of
35:35offices.
35:37If there'd been no road between the rings, the blast forces would have continued wreaking havoc through at least one
35:43more solid ring of offices, killing more people on its way.
35:51But other features of the building also saved lives.
35:54To see them, we need to rewind to the moments after impact.
36:00Marilyn Wills and those in the human chain crawl across the first floor to escape.
36:05They're directly above the crash zone.
36:08Concrete columns are blown apart and obliterated.
36:12But remarkably, the first floor remains standing for 19 minutes before it finally collapses.
36:19In these precious moments, Marilyn and her fellow survivors reach the window.
36:25The whole investigation now focuses on understanding why this part of the building withstood a jet going at 850 kilometers
36:32an hour and why it didn't collapse upon impact.
36:36As investigators map the area, they find that 30 of the ground floor columns were wiped out and another 20
36:43severely damaged.
36:45Structural engineers are mystified.
36:48With so many columns knocked out or damaged, what held up the building?
36:52They look back to 1941.
36:59Construction on the Pentagon began on September 11, remarkably exactly 60 years before the terrorist attack.
37:08At the time, War Department officials believed there'd be no need for such a massive war headquarters after World War
37:14II.
37:15The building would become a warehouse for files.
37:18To support the heavy loads, construction workers put in extra beams and columns, and they added extra steel reinforcements.
37:27After 9-11, the Pentagon's lead reconstruction engineer, Alan Kilsheimer, built an exact replica of the 1941 beam and column
37:35system found inside the Pentagon.
37:39If you blew this column out right here, what would happen is, this beam would say, there's nothing holding me
37:45up anymore, and it would say, geez, I better go along this steel line over to the next column and
37:50see if I can carry myself to the next column.
37:53The fact that these bars were doubled up like this, either in the bottom or the top, allowed that to
37:57happen.
37:59Kilsheimer took a closer look. Each column contained a continuous piece of reinforced steel, from floor to ceiling.
38:07What this does is, this stops these bars from bending outward, and it stops the concrete from in here, from
38:14coming out of this cage.
38:17As the catastrophic forces raged through the ground floor of the Pentagon, they destroyed 50 columns along the path of
38:24destruction.
38:26But it's the reinforced steel within the remaining columns that kept the building up.
38:33This wouldn't happen in today's construction. What happens is, if one of these breaks, the whole thing doesn't fail, while
38:40on a new building, if one or two of those break, the whole column could blow out.
38:44But investigators discovered another feature of the 1941 design, which also saved lives.
38:51Three minutes after the explosion, Bobby Hogue and his colleagues on the third floor came across a crack in the
38:57floor.
38:59Then I stepped over what was the expansion joint that bisected our office, and that's when I really became aware
39:07of, that the building was in a state of collapse, about to collapse.
39:12Because it was clearly broken open, the floor had just cracked in half.
39:17The reason? The Pentagon's original designers added structural features called expansion joints.
39:24These joints accommodate the expansion and contraction of the building through the seasons.
39:29They allow room to expand in the heat of summer, and contract in the cold of winter.
39:35Because of these expansion joints, the Pentagon behaves like a series of separate buildings.
39:42So on September 11th, the expansion joint on the Pentagon's west side protected the rest of the building, and ultimately,
39:49saved lives.
39:52Nineteen minutes after impact.
39:59The Pentagon looks as though a knife cut it right at the expansion joint.
40:05Had this not been an expansion joint, and this would have been originally connected from this side to this side,
40:11we would have lost a much larger piece of the existing building north of the expansion joint.
40:18The expansion joint bought time for the survivors to make their way to safety.
40:26If you're going to have to go through something awful like this, you know, the Pentagon is as good a
40:32place to choose as any.
40:36God forbid you should ever have to make such a choice, but if you have to, you want to choose
40:41that place.
40:43On 9-11, the Pentagon heroically withstood the extreme forces on its structure.
40:48But investigators found yet another reason why so many people survived.
40:54These windows.
41:01Investigators are uncovering the secrets of how the Pentagon withstood the 9-11 attack, and how so many people survived.
41:09When the plane hit the Pentagon's west side, Bobby Hogue looked out the window and saw fire engulf the building.
41:16But that fire never touched him. Why?
41:19The answer was right in front of him, in the window.
41:23If someone had come to me in 2000 and said, we need to put a bomb-proof window in your
41:29office, I'd have said, get out of here.
41:30What are we going to do with a bomb-proof window, you know?
41:33Well, guess what?
41:36Yeah, sure came in handy.
41:38In 1995, 168 people died in the Oklahoma City bombing.
41:43This and other acts of terror on office buildings taught building experts vital lessons.
41:53Engineers came up with improvements, including tougher windows.
41:59So where there were blasted stone windows, people were able to escape, especially on upper floors.
42:07These windows, just meters from the plane's entry point, are still intact.
42:12Without them, Bobby and hundreds more Pentagon workers could have died.
42:19By 9-11, the Pentagon had installed these life-saving features into an area of the building known as Wedge
42:251.
42:26When the terrorists lock onto their target on the morning of September 11, it's this renovated section that appears in
42:33their sights.
42:34But the Pentagon renovation program also saved lives in ways no one could have predicted.
42:41On 9-11, the plane enters the building diagonally into Wedge 1, but continues wreaking havoc into another section known
42:50as Wedge 2.
42:53Normally, 5,000 people work in this space, but by September 11, renovation of this second wedge was underway.
43:02Three months earlier, most of the 5,000 employees who work in Wedge 2 were relocated to temporary offices elsewhere.
43:11Had this been in another area of the building, there could have been tremendously higher, ten times the amount of
43:17losses.
43:18Much more on the magnitude of New York City.
43:24Finally, investigators piece together the tragic course of events.
43:298-20, American Airlines Flight 77 takes off from Washington, Dallas Airport with 53 passengers and six crew aboard.
43:398-56, hijackers turn off the aircraft's transponder, air traffic control loses Flight 77.
43:499-38, the Boeing 757 flies into the ground floor of the Pentagon.
43:54In milliseconds, the aircraft begins to disintegrate.
43:59Fuel spews through the building.
44:02Violent fires and explosions track the plane's brief but deadly journey.
44:089-39, the sturdy 1941 construction with expansion joints and blast-proof windows withstands the impact.
44:16Allowing many Pentagon workers to make their way to safety.
44:229-57, only one-fifth of the area hit, collapses.
44:29All the passengers and crew and 125 Pentagon workers perish.
44:36The heroism of the Pentagon employees themselves saved countless lives.
44:44Any service member, a soldier, airman, marine, it's something in you that you never leave your comrades.
44:53When that lady grabbed the back of my pants, I believe that was the best thing that happened to me
44:58that day.
44:59I was no longer responsible for Marilyn Wills.
45:01I was responsible for her and all of those people who followed her.
45:13A memorial inside the Pentagon is etched with the names of all those who lost their lives in the disaster.
45:24All military personnel wounded that day were awarded the prestigious Purple Heart.
45:31The disaster of 9-11 has changed the way we think, travel, and the way we design buildings.
45:39From ruin and heroism on 9-11, construction crews in only one year rebuilt the damaged area on the Pentagon's
45:46west side.
45:48It was a huge pride thing and still is to this day for everybody.
45:51That building is such a symbol of America's strength and we've healed that building.
46:01The new walls restore the imposing appearance of the five-sided fortress.
46:06The Pentagon not only protects the United States in times of danger.
46:10The building itself provided the ultimate protection for thousands of Pentagon workers during a day of terror.
46:18But one scar in the facade remains.
46:21A block of Indiana limestone, still blackened by the fire from the attack, with a simple inscription.
46:29Its dark face is a dramatic contrast to the bright new limestone.
46:34But it's a chilling reminder of the events of that tragic day.
46:58It's a positive intention of the world.
46:58That moment we take to the beginning of the day of the Sakai H catch.
46:58Once this section of the discovery has changed the fact that we have shown through the flying screen that the
46:58light of the sky.
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