I have been spending the last few hours trying to come up with a way to compare the explosive forces between the '93 bomb and the plane impacts of 2001. However, my lack of expertise in this area of physics, pertaining to kinetic energy, explosive force, pressure, etc. is preventing me from making any sort of informed conclusion. On the other hand the information I have gathered suggests ( and I use that term lightly) that a bomb ( on the order of magnitude used in the '93 bombings: The bomb exploded in the underground garage at 12:17 P.M., generating a pressure estimated over one GPa (Giga Pascal) and opening a 30-meter-wide (98 foot) hole through four sublevels of concrete. The detonation velocity of this bomb was about 15,000 ft/s (4.5 km/s). Source: http://en.wikipedia.org/wiki/World_Trade_Center_1993_bombings#Bomb_characteristics) planted in the sub-level basement (which houses the critical main support for the tower) had a much larger probability of collapsing the building than an impact of a 767 carrying 10,000 gallons of jet fuel nearly 1,000 feet up from the basement. If anyone feels they could expand upon this with more scientific basis, it could be a nice lesson in logic for those who say the towers were bound to collapse after the plane impacts. Any thoughts?