Originally Posted by MediaGuy

Actually, in the allotted time, the fuel could not have weakened the steel columns and girders.

NIST has admitted that none of the temperatures in the buildings could have risen much above 650 degrees. Which is not even one-third enough to weaken steel, and which would require hours of exposure to cause softening (at much higher temps).

The Planes couldn't have damaged the structural integrity of the buildings because they were largely aluminum. The engines, made of titanium and other hard alloys, could have taken out some of the central columns. However, this is largeley and admittedly speculation on the part of NIST, and would not have engendered global collapse.