Joe Casaliggi, NYC firefighter: "You have two 110-story office buildings. You don't find a desk, you don't find a chair, you don't find a telephone, a computer. The biggest piece of a telephone I found was half of the keypad, and it was about this big. The building collapsed to dust."
This is very clearly a case of controlled demolition. When a building collapses due to structural failure, like when a building collapses because of an earthquake, it doesn't just disappear to dust.
Here is a picture of a bridge in Lebanon that was hit with Israeli missiles last summer. Note, it fell further than the height of one floor of the WTC towers and had a missile propelling it down at a faster than gravity rate, yet the concrete did not turn to dust upon hitting the ground. Supposedly the concrete in the WTC towers turned to dust after falling the height of a mere floor's distance with only gravity pulling it down. And supposedly even though it turned to dust it somehow managed to sever all 47 core columns every few floors.