The most striking thing about the 9/11 commission report chapter 9 "Heroism and Horror" is how much worse things might have been if the world trade center had not been attacked in 1993. As a result of the earlier attack people in the WTC were extraordinarily prepared.

P 316 "Several factors influenced the evacuation on September 11. It was aided greatly by changes made by the Port Authority in response to the 1993 bombing and by training of both Port Authority personeel and civilians after that time. ... The general evacuation time for the towers dropped from more than four hours in 1993 to under one hour on September 11 for most civilians who ewere not trapped orphysically incapable of enduring a long descent."