I'm not a scientist, but from my understanding they would disintegrate. I believe this has to do with the resonant frequency of the metal in question. Note the pictures on Dr Wood's site..... many unburned papers, no reports of burned bodies on the streets surrounding the towers. It wasn't that hot!!
In other words, you are only attempting to push emotional buttons, here, not further understanding. I think you've read some exaggerated claims that included words like "resonant frequency" and, since they had an effect on you, you are tossing them out here in the hope that someone else will be suckered, too. Think logically about this for a moment. You are claiming that engines have disappeared from cars and from a fire engine. The cars are most likely gasoline engines, while the fire engine uses a diesel engine. The composition of the engine blocks is different. They don't use the same materials. Why would there be a resonant frequency common to engine blocks of differing materials that would not be shared by the metal frames of the cars?
As others have already asked, what is to be gained by theorizing on exactly which specific technology was used to bring down the towers? The mere fact that the towers were apparently dropped in a controlled demolition of some sort is enough. That fact is undeniable simply because the tops of the towers could NOT have dropped at free-fall speed without demolition of the floors below to clear the way. An explosion cause by something like thermite seems pretty likely as it would also have created a vacuum underneath, reducing air resistance to the fall.
Isn't it interesting, though, that will all of that data available at any Blockbuster (just rent a 9/11 documentary and time the fall of the towers for yourself) the Pentagon is still rarely mentioned? The fact is, everyone did see the planes fly into the towers. That gives a great cover story that most will accept for the events of that day. How many people saw a 757 fly into the Pentagon? None. The original eyewitness reports were of a smaller craft roughly the size of a business jet that made a whooshing sound rather than the characteristic roar of a commercial jet.
I've looked extensively at both events. For my money, the Pentagon event is the one to focus on.