Again, if there MUST be a conspiracy about this, why not just have the Evil Overlords(tm) place a device on the plane to remote control it from their base in the hollow mountain and actually crash a 757 in to the building? That would eliminate most of the anomolies in the story, and still allow for a reason to be paranoid.

I thought bin Laden was the Evil Overlord(tm) controlling his suicidal minions from his base in the hollow mountain (or cave)?

Again, as I said before, it may have been concluded that using an actual 757 would not be successful in being able to create the damage they wanted. Or that a remote controlled 757 could even hit the Pentagon without the risk of hitting the ground before reaching the wall, etc.

Why they would use cordite, or why they would not use an actual 757, are points of speculation. But they are not evidence against a conspiracy.