[Tares]

I suspect that as the airliners passed through the buildings they also heavily damaged the interior core (and likely severed exist stairs to those trapped above the impact points).

If you live in New York, you should know by now that there are many people who were on floors ABOVE the crash points who were able to escape to ground level before the towers collapsed.

[finnman69]

yes, people likely got out of the second tower to be hit BEFORE the second plane hit. But I also read account that at least one of the exit stairs was blocked and that the internal concrete walls flexed several inches. People who got out were DAMN LUCKY.