From the Discovery Channel:
The twin towers of the World Trade Center would probably be standing today if the impact of the planes used in the Sept. 11, 2001 attack had not destroyed fireproofing material, experts said Tuesday.
After what it described as the most detailed examination of a building failure ever conducted, the U.S. Commerce Department’s National Institute of Standards and Technology (NIST) said it would be suggesting major changes to the way skyscrapers are built and managed…
If the fireproofing had remained in place, Sunder said, the fires would have burned out and moved on without weakening key elements to the point of structural collapse.
More here.