"We were looking out the window and the entire sky was filled with paper," she said. "We thought it was a ticker tape parade."
Then, Keeling said, she noticed a huge cloud of smoke billowing from the north tower. "Fireballs were falling to the ground, which I now know were people."
Keeling and the other trainees headed for the stairs. When they were between the 59th and 58th floors, a voice on the building's public address system said the north tower was the only structure in danger and that everyone could return upstairs. Half of her group went back up. She and others continued to the street.
"People were coming down from the top floors in every condition you could imagine," Keeling said, through tears.
"I heard a woosh like air getting sucked in a vacuum. I grabbed my jacket and got as close to a planter as possible and started feeling little things on my back like hail, and they got bigger and bigger until the air was solid debris."
Keeling said she turned to a man who walked down the stairs with her and asked: "Are we dead?"
She said only 75 of the people who attended her training group were accounted for.
Denny Levy, 36, a videographer, witnessed the impact from the ground.
"I saw this plane flying low over the buildings down the center of Manhattan," said Levy, who was uninjured. "It went toward the World Trade Center. It sounded like its engine was broken. Your brain tricks you. I thought it went past the building, and then it went a little to the left and took a plunge at the building.
"Then there was this burst of stuff coming out of the building. There was no fire and no explosion. I wondered why the plane was making so much noise and was so low.
"You could tell it was a passenger plane, that it was in trouble or trying to get close for a view. You'd never think a plane would go dead center into a building. It was like a missile.
"I thought it was an accident, except he took a sudden left. He went right for it. It was so creepy. I thought, 'Oh my God, I just saw 300 people die.' "
John Kelly, 38, a furniture designer, said he looked out a window of his apartment after hearing the first explosion.
"My wife says, 'Oh, my God, they hit the second building.' I looked. The plane went through the building, and there was a blast out two sides. It was like exit wounds in all directions.
"I saw people jumping, bodies flying through the air. I saw people waving white flags. It was horrible.
"Police and ambulances were everywhere, and within seconds there was no one. You saw everyone running, running, running. You saw shoes, sunglasses on the street. People dropped their stuff and ran.
"It was like a nuclear explosion."
A Crushing Blow to Symbol of Strength
As a stunned nation attempted to grasp the horror of television images from New York, a third hijacked airliner crashed into the Pentagon, bursting into flames and delivering an incendiary blow to the symbol of America's military might.
American Airlines Flight 77, a Boeing 757 with 58 passengers and a crew of six aboard, hit the west side of the building at 9:41 a.m. EDT, half an hour after it left Dulles International Airport en route to Los Angeles.
"I glanced up just at the point where the plane was going into the building," said Carla Thompson, who works in an Arlington, Va., office building about 1,000 yards from the crash.
"I saw an indentation in the building and then it was just blown-up up--red, everything red," she said. "Everybody was just starting to go crazy. I was petrified."
Within 20 minutes of the crash, the White House, the Pentagon--the world's largest office building--and the U.S. Capitol were evacuated.
What began as an orderly exodus from the nation's defense headquarters turned to panic as evacuees made their way to parking lots.
"People were just milling around in a daze," said Ginger Groeber, a civilian Defense Department official who had been in the Pentagon watching television reports of the attacks in New York when the building was hit.
"These people were panicking out there," she said. "People were looking for their staffs. Nobody's cell phones were working."
The District of Columbia government shut down. Many private firms also closed and sent employees streaming home, causing traffic nightmares.
As parking garages closed and cars poured out, one woman grabbed the door of a lone car going in.
"Don't park," she yelled, her face twisted in fear. "They're hitting the Pentagon! They're hitting the Pentagon!"
Naval officer Clyde Ragland, who works near the Pentagon, was stuck in his office because the streets outside were clogged with traffic.
He and his co-workers were watching television reports of the disaster in New York when "we gazed out our own windows and, to our horror and disbelief, saw huge billows of black smoke rising from the northeast, in the direction of D.C. and the river . . . and the Pentagon."