Never mind her asthma, Carla Bonacci recalls thinking on Sept. 11, 2001, after her PATH train from New Jersey got diverted from her World Trade Center stop to a station about a mile north.

The Port Authority of New York & New Jersey manager, seeing smoke billowing from the 110-story twin towers of the WTC, raced toward the infernos. She was hell-bent on getting to her team, housed on two floors high in the north tower. Just before she made her destination, the south tower collapsed. To her, it sounded like a bomb and brought back vivid memories of the first terrorist attack at the WTC, on Feb. 26, 1993.

Of the 84 port-authority employees killed on 9/11, 16 were in the World Trade Dept., where Bonacci had worked since 1987. “World Trade was my family,” says the 29-year port-authority veteran. “That's why I ran back,” she adds. “I felt I needed to be there.”

In the chaos, Bonacci then set her sights on finding the port authority's West Street command-center van. She was in the van when the north tower collapsed. More chaos ensued. She raced up the street, trying unsuccessfully to outrun the north tower's giant debris ball bearing down on her. She ended up burying her head in the jacket of a firefighter. They both got covered with soot.

As assistant director for infrastructure and development, Bonacci is currently charged with overseeing implementation of the guidelines, which she helped craft, in the master plan for the WTC's $19-billion redevelopment. She asked for the assignment. “Working on this project is my healing, I think,” says Bonacci, who worked on the WTC upgrade after the 1993 attack. “Seeing it one way and seeing it rebuilt another way is very important to me,” she says.

Brian Lyons, from the time he was a kid, viewed the twin towers as icons. He had even achieved a longtime dream on Sept. 12, 1990, when he proposed to his wife at the Windows on the World restaurant atop the north tower.

Lyons was working on an interiors project in midtown Manhattan when he learned that planes had crashed into the towers. He watched them collapse from afar, with the sinking feeling in his gut that his kid brother —a firefighter with Squad 41 in the South Bronx—was at the WTC. Lyons made his way there to look for Michael (see sidebar), who did not survive. But he knew from the moment he arrived he would stay to rebuild. Currently, he is a project manager on the WTC Transportation Hub for the local joint venture of Tishman Construction Corp., a unit of AECOM Technology, and Turner Construction Co. “We don't want to call it Ground Zero,” he says. “We call it the World Trade Center.”

Native New Yorker Salvatore Adinolfi was 1,054 miles from the WTC on 9/11, living in Boca Raton, Fla. Like millions of Americans and people the world over, Adinolfi watched the day's news footage in horror and disbelief. He remembers “a powerful feeling of helplessness, being so far away from home.”

When a call came in July 2010 summoning him to come help speed the work pace on the National September 11 Memorial & Museum so that the plaza could open by the 10th anniversary of the attacks, Adinolfi packed his bag. He was determined to do what he could for 9/11's 2,983 victims and their loved ones.

Adinolfi tries to fly home every couple of weeks to see his wife and two teenage sons. “It's a sacrifice for my family,” he says, “but we all agreed to do this.”

Structural engineer Leslie E. Robertson has a very different kind of 9/11 story. Beginning in the 1960s, Robertson served as the project manager for the original WTC complex, as part of a team formed by the late structural engineer John Skilling. After construction of the complex, Robertson became the structural consultant to the WTC. Besides years of routine work, he led the emergency fix and permanent repairs to the deep basement after the 1993 bombing.

Robertson, currently 83, was involved with the WTC for nearly 40 years by Sept. 11, 2001. On that day, he was in Hong Kong, 14,000 miles from home and his office, which overlooks the WTC.

Devastated about the lives lost, Robertson headed back to New York City to offer guidance to the rescue-and-recovery effort. When he arrived, he learned there was little he could do at Ground Zero to add to his colleagues' work. Instead, he met with some of the mourners.