Located on the south side of the Potomac River opposite the city of Washington, DC, the five-sided Pentagon building is a massive symbol of US military power.
For the roughly 23,000 military and civilians who go to work there, September 11, 2001, started out as another day of routine.
The heat of summer was fading and the weather was cooling amid the first signs of approaching autumn. The sky was clear blue.
“It was just a beautiful, normal day coming to work at the Pentagon.” said Army Colonel Marilyn Wills, a congressional affairs officer who was sitting at a conference table in a meeting when a commercial airliner struck the Pentagon.
American Airlines Flight 77 carrying 64 people including five al-Qaeda hijackers crashed into the west side of the Pentagon at 9:37 in the morning. Two other hijacked planes crashed into the twin towers of the World Trade Center in New York City and a fourth fell in a field in Pennsylvania.
The events killed nearly 3,000 people and set off a rapid deployment of US forces to Afghanistan, beginning the US’s longest war.
Wills, age 40 at the time, was blown across the room to the floor by the blast. She guided others out, crawling along the floor through smoke and searing heat to a window, their clothes melting to their bodies, smoke choking their lungs.
Some made it out of the chaos and smoke and burning jet fuel, some did not. Twenty-nine people inside the Pentagon were killed that day.
Wills was lifted out of the building by people on the ground who formed a human ladder to reach the window. Hospitalised for burns and smoke inhalation, she returned to work 13 days later and learned the blast had been an attack.
“When I came back the worst thing was the smell. You could smell the fumes, you could smell the burning bodies, you could smell the burning wires. You could smell it all,” Wills, now retired from the Army, recalled at a Pentagon briefing on Wednesday.
“I walked down the hallways and I would think that I saw ghosts,” said Wills who was later awarded a Purple Heart for her injuries and the Soldier’s Medal for heroism.
Roy Wallace, who was assistant deputy chief of staff for the Army, was 50 feet from the path of the aeroplane crash. He vividly recalls the fire sucking the oxygen out of the room where he was.
An officer staggered out of the fire and fell to the ground in front of Wallace, his uniform “a molten blob”. Lieutenant Colonel Brian Birdwell was yards from the plane when it hit. He was engulfed in flames.
Wallace later retrieved a clock from his office. It had stopped 19 minutes after the time the plane struck.
“That’s how long it took for the heat of the flames to melt the crystal, forever freezing the hands in time,” Wallace said at Wednesday’s media briefing.
With the building still smouldering and the US on high alert, the Army’s focus quickly turned to preparation for deployments to Afghanistan, recalled Mark Lewis, acting secretary for manpower and reserve affairs at the time.
“We transitioned to war immediately. We got very busy with that,” Lewis said.
Gerry Kitzhaber, a deputy assistant secretary, narrowly escaped death by chance. His wife had called to tell him about the plane crashes in New York, delaying him from going to a meeting. He would have been in a corridor hit directly by Flight 77.
“We only spoke for a few minutes and I hung up the phone and just as I turned around, the plane hit,” Kitzhaber recalled.
Kitzhaber evacuated to the Pentagon’s centre courtyard where he saw a fragment of the aeroplane’s fuselage “about the size of turkey platter” on the ground.
“We knew at that point, clearly we had been hit by an aeroplane.”
Evacuating in a stampede of people out of the building to the street, Kitzhaber encountered a delivery truck driver who had witnessed the crash.
“I heard a noise, I looked up and saw the plane coming in,” the truck driver had said, according to Kitzhaber.
“And the son of b***h gunned the engines just before he came in,” said the truck driver who could see the people on the plane through its windows.
Moments later, two Air Force F-16 fighter jets, scrambling out of Bolling Air Force Base across the river, screamed over the building en route to intercept United Flight 93 which crashed in Pennsylvania when passengers stormed the cockpit.