What’s unreasonable in thinking that a plane that has hit a building at the top of it shouldn’t make the whole building collapse in just a matter of tens of minutes? If anything, this war in Ukraine has proved that buildings can sustain a lot and lot of damage until structurally collapsing.
I can't think of a single example in Ukraine of a building experiencing anything remotely similar to the sustained heat of 24.000 liters of aviation fuel burning and spreading throughout the building by way of the elevator shafts.
Buildings are great at surviving individual impacts and explosions. They're not so great at aviation fuel melting through the concrete and steel supports and weakening them over time.
If Russia started indiscriminately dumping thousands of liters jet fuel inside buildings and setting it on fire, we might see something remotely similar to what happened on 9/11. Until then, I don't know why Ukraine has any bearing on what happened back then.
