"It Was Like Watching Television"

"My first thought was that it was an accident, that a little airplane was involved," Plumer recalls, echoing the initial reaction of many Americans.

Plumer walked across the office to the other side of the building and watched, incredulously, as a second explosion rocked the other tower.

"I still didn't think much of it until someone yelled, 'There's another plane,' " he says. "It was like watching TV, watching a movie. The explosions just kept getting bigger. I thought maybe a helicopter had gotten too close.