Reply #41: Bad analogy...

[Carefulplease]

If you drop a ton a loose sand in air from a hundred feet, the sand will disperse and traverse a volume of air that is possibly heavier than one ton (Air weigh about 1gh/m^3).

When the towers collapse, the only air resisting is the air within them. This is roughly 1,600,000kg of air. This only represents 0.5% of the mass of the towers (around 300,000 tons each). The resistance this would provide to the falling tower would be negligible even had they wholly turned to dust in an instant.