I have never believed any of the buildings fell because of impact, or that the steel girders melted. Liquid pools of steel and iron don't happen from a falling girder, and floors do not collapse in free-fall, and Building 7 was barely charred when it was pulled.
If they lie enough, it becomes fact. I'll look at DEW as a possibility but my current guess is that the nanothermate melting of the structural elements was the cause.
I would believe it was an attack of evil fairies before I will that it was the temperature of burning av fuel in open air melted those sealed beams.
One of my trigger points....
I'll check it out.