World Trade Center Engineer Leslie Robertson on 9/11 Attack, Building Collapse

Leslie Robertson, one of two engineers who designed the World Trade Center, was in Hong Kong when he first learned of Tuesday's terrorist attacks. Before the second plane even hit, he was on his way to the airport.

Forty-eight hours later, Robertson, founder and owner of Leslie E. Robertson Associates in New York, has only gotten as far as Tokyo. He's still struggling to get home to his family in Manhattan, and the project he spent 10 years designing and perfecting.

"Beyond the reaction that any citizen has-the sadness that we all feel -- you have to understand, I worked long hours, seven days a week on this project back when I was young and energetic," says the 73-year-old, his voice breaking with emotion. "It was just terrible to watch, painful and horrible."

Still, Robertson, whose firm is responsible for three of the six tallest buildings in the world, feels a sense of pride that the massive towers held up as well as they did -- managing to stand for over an hour despite direct hits from two massive commercial jetliners.

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"If they had fallen down immediately, the death counts would have been unimaginable," he says. "The World Trade Center has performed admirably, and everyone involved in the project should be proud."

The buildings were designed specifically to withstand the impact of a Boeing 707 -- the largest plane flying in 1966, the year they broke ground on the project -- and Robertson says it could have survived even the larger 767s that crashed into the towers on Tuesday morning. But the thousands of gallons of burning jet fuel finally brought down the noble structures. "As the fire raged it got hotter and hotter and the steel got weaker and weaker," he says, adding that building a skyscraper able to handle such a blaze would not have been viable, financially and functionally. "You could always prepare for more and more extreme events, but there has to be a risk analysis of what's reasonable."

As for the 1993 bombing, Robertson says,"I felt like we had taken their best shot." For now, he's not ready to even contemplate rebuilding but hopes our collective sense of security returns soon. "We just have to hope that this country doesn't turn into a fortress in order to deal with people like this."

Editor's note (published July 1, 2010): This article originally stated that each of the World Trade Center buildings included a reinforced concrete core. After being alerted to the error in June 2010 by readers, NEWSWEEK contacted Robertson, who confirmed that there was no concrete core in either tower. "For both towers, the structure of the core was composed of steel beams and girders supported by steel columns," he said. "The steel beams and girders supported a profiled metal deck overlain by reinforced concrete slabs." NEWSWEEK regrets the nearly decade-old error, but is glad to set the record straight, particularly since new readers are still finding the story.

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World Trade Center Engineer Leslie Robertson on 9/11 Attack, Building Collapse | U.S.