The destruction of Building 7 exhibited numerous tell-tale signs of a conventional controlled demolition:
* The building sank into its footprint at near free-fall speed.
* The remarkably short rubble pile was mostly confined to the building's footprint, with exterior wall sections lying on top.
* The destruction produced a cloud of dust with at least the volume of the building.
The destruction of each of the Twin Towers differs from a conventional demolition in several respects:
* The destruction proceeded from the top down rather than from the bottom up.
* The time to complete destruction was about 50% longer than free-fall time.
* The destruction was hidden behind a descending mushrooming cloud of pulverized materials and metal pieces.
* The rubble pile was spread out, the vast majority of the fallout lying outside the towers' footprints.
* The destruction produced a cloud of dust that continued to grow after the last piece of steel hit the ground, when it was already twice the volume of the building.
If the destruction of Building 7 is explainable as a conventional demolition, then perhaps the different features of the Twin Towers' destruction are explainable as modified controlled demolitions, in which far greater quantities of explosives are used, and the charges are set off in a top-down instead of bottom-up sequence in order to simulate "progressive collapse" from the crash zones.
The main differences between the destruction of Building 7 (and conventional demolitions) and the destruction of the Twin Towers can be summarized as follows:
* The Twin Towers were destroyed from the top down instead of either from the bottom up or simultaneously throughout.
* The Twin Towers were destroyed much more thoroughly than buildings destroyed by conventional demolition.
* The destruction of the Twin Towers killed over a thousand people.
Because of these differences, most people less readily entertain controlled demolition of the Twin Towers than they do of Building 7. Ironically, the first two differences actually support a stronger case for the controlled demolition of the Twin Towers than Building 7. Their more thorough destruction required the input of more destructive energy, and their top-down sequence of destruction meant that less mass was available above the collapse zone to accomplish this greater degree of destruction.