Get some news footage that keeps watching the building. The supposed demolitions are going on the whole time, a lot of stuff happensï»¿ when a structure is nailed by an airplane fueled to travel 3000 miles. Fuel pours like napalm down the elevator shafts igniting fires all over. Either way, the collapses clearly occur at the point of impact in all videos seen. The inertia from there made it impossible to stop, it didnt need help.