SImple physics disproves this. The building is designed at all times and all places to hold the weight above. A little jet fuel at the 89th floor, hypothetically weakening certain parts of the steel structure and leading to partial collapse, would pancake no more than 4 to 5 floors below the 89th floor.

Then the engineered support, which always and in all places, is designed to hold floors 85-101, would stop the collapse. The jet fuel which is about as threatening as Sterno is long burnt off.

You have to look at the fact that no steel building has EVER burned down, and the amount of jet fuel is dinky compared to the mass of the buildings. There are some excellent graphics demonstrating this.

SImple physics disproves this. The building is designed at all times and all places to hold the weight above. A little jet fuel at the 89th floor, hypothetically weakening certain parts of the steel structure and leading to partial collapse, would pancake no more than 4 to 5 floors below the 89th floor. Not every last part of the building.