They deliberately took the markings and windows off the jet so it wouldn’t be harder to watch than it already is. Here’s arguably the darkest half-second in American history, instant by instant, with assorted variables isolated and then recombined so that you can see the full effect. The model of the plane was separated into hundreds of thousands of components so that the computer could give each one its own trajectory after impact.

Contrary to what certain unemployed chat-show hosts might tell you, it was the fuel that did the most damage:

Sozen says the actual damage to the building’s facade that was observed was identical to the damage shown by the numerical simulation…

“The aircraft moved through the building as if it were a hot and fast lava flow,” Sozen says. “Consequently, much of the fireproofing insulation was ripped off the structure. Even if all of the columns and girders had survived the impact – an unlikely event – the structure would fail as the result of a buckling of the columns. The heat from an ordinary office fire would suffice to soften and weaken the unprotected steel. Evaluation of the effects of the fire on the core column structure, with the insulation removed by the impact, showed that collapse would follow whatever the number of columns cut at the time of the impact.”

Click the image to watch. The link at the upper left worked for me; the one included in the body of the text didn’t.