You keep asking about controlled demo...If my company were hired to do a demo (which we aren't a company that does that, but would only require a few certs on top what we already have to do so) here is how I would do it.
I would use the fact the building was almost vacant and prep for months or a year the buildings in advance. (Remember, most foot traffic in the buildings was from Subway traffic below. Buildings only became 70 percent occupied months before the destruction with companies that just "appeared"..And some how many of those same companies helped with the clean up and removal of materials after the destruction...CCA public records).
I would wire shape charges in lower levels (1000s of reports of explosions) reversed directional on the I beams, standard in cuts on the outers.
Upper levels, I would run thermite in a horizontal v in staggered directions varying ever 4th floor. Capped with a small load c4 charge on each v converged tail.
I would use the planes/missles ECT as a diversionary tactic..No different than a magician. After letting that simmer for a bit, I would then drop the towers. Controlling from building 7, I would start the sequence...First hit the thermite for show and weakening..(reports of liquid metal 3 minutes before collapse.)..
Then timed upper c4 charges to blow out the cut Vs....Then hit the shape charges on the ground floors...Then the mid floors c4...And down she comes.
Rinse and repeat....
Then when all looks good, do the same with evidence/building 7 and hope no one asks why the hell that one fell (should have thought the last one through)
Beauty of a cut...But thermite is very nasty burning and leaves a ton of slag..
It would be a work of art if it wasnt the essence of evil...