People working inside felt the building move, but didn't know what was happening, according to reports. No alarm bells sounded. No public address announcements were made. Workers didn't know if they should evacuate or stay in the building.
When they did evacuate, they found themselves crammed into pitch-black stairwells filled with a thick, choking smoke. They bumped into walls and each other in the darkness.
The World Trade Center did have an emergency plan for the evacuation of workers and visitors. Two or three times a year the plan was put into practice. But these plans became useless when the explosion destroyed the Port Authority's command and operations centers. (The Port Authority of New York and New Jersey built, owned and operated the World Trade Center, where it maintained its headquarters.) The blast knocked out electricity, telephones, closed-circuit television monitors, and the public address system.
It took six hours for occupants to escape the building on that winter day. Some people were stuck in elevators for ten hours.
Changes to the planAfter the 1993 bombing, the World Trade Center made improvements to facilitate more efficient evacuations. Batteries were added to every other light fixture in the stairwells in case power went out as it did in 1993. Handrails were painted with yellow glow-in-the-dark paint - which also marked a continuous stripe down the middle of the staircases. Bright arrows were added to guide people along corridors to stairway connections.
The Port Authority installed loudspeakers so building managers could talk to people in their offices as well as in hallways. It gave every disabled person an evacuation chair that would let two strong men carry them downstairs. One evacuation chair was used to carry a man down from the 67th floor on September 11th.
Most importantly, building management took evacuations seriously. Drills were held every six months, sometimes to the irritation or amusement of occupants. Each floor had fire wardens - sometimes high-ranking executives of a tenant - and they were responsible for organizing an evacuation on their floors.
These steps proved critical for saving nearly 20,000 lives September 11th. In 1993, it took six hours to evacuate most of the occupants of the trade center. On September 11th, the evacuation took only two hours.
Just listen to the comments of survivors. George Sleigh and Claire McIntyre, who worked for the American Bureau of Shipping, located on the 91st floor of the North Tower, described their department's reaction. "There were about 11 of us in the office at that time of the day, and so we just made sure that everyone was accounted for that should have been there and decided to get out as quickly as possible," said Sleigh.
"When we first came out of our office, we knew there was a stairwell just to the left of our office," said McIntyre. "And that's the one we looked at first. It was open. It looked passable."
Christine Gilles, who worked for Thor Tech on the 87th floor of the North Tower, said, "I was with my three other co-workers when we entered the stairwell to make our way down. There was a sense of panic, a sense of urgency, but we were very focused on just getting to safety and getting out of the building."
"I think the training and all of the fire drills that we had in the World Trade Center really did prepare us to not panic and to know where the stairwells were for one thing, and going down the stairs to keep calm," said McIntyre.
"We had appointed fire marshals on the floor. And each one was responsible for a certain section of the floor. We had searchers to go into the bathrooms when the fire drills were happening," explained Sleigh.
"I just feel that I was very fortunate, that somehow God was protecting me and preserving me for some reason," said Sleigh. "Whatever that purpose may be, I don't know, but I'm just so very thankful that my family did not have to go through the grief that so many other families had to go through. And just a sense of gratitude for that."