all im going to say, is that the twin towers are the first concrete and steel made buildings in history to collapse through fire.
Exactly, that was brought up on more than one occasion but the problem was that this was linked to conspiracy theories. Iirc one suggested these were long term plans where a building is constructed using sub-standard gear, corners are cut etc & where the building would normally last many, many years these would drop to bits long before then - leaving a few very embarrased people - hence the 'attack'.
Another, along similar lines suggested this was done as an insurance job - but again, suggesting corners cut.