We have been lied to.
The first lie was that the load of fuel from the aircraft was the cause of structural failure. No kerosene fire can burn hot enough to melt steel.
But let's suppose that the fire was hot enough to melt steel. What would have happened in that case? Before it breaks, hot steel begins to bend. This redistributes the forces in the structure and puts elastic stress on those parts that are still cool.
The process is asymmetric, so that the structure should visibly bend before breaking. But of course, no steel skyscraper has even bent over in a fire.
Let's suppose the structure were sufficiently weakened that it did fail catastrophically near the point of the airplane strike.
In this case, the intact structure below would exert an upward force on the base of the upper story portion of the building (the part that has been broken loose), while any asymmetry would allow the force of gravity to work uninhibited on the tip of the skyscraper.
Thus, the top section of the skyscraper would tip and fall sideways.
How it was done.
The World Trade Center was leased by Westfield America and Larry Silverstein, on April 26th, 2001. Zim Israeli Shipping moved out of the buildings around that time.
With a certain amount of shuffling of tenants from floor to floor, it should have been easy (with all the commotion and noise of remodeling) to plant explosives on several floors; enough for at least a sloppy kind of controlled demolition.
AttackOnAmerica.net - Proof Of Controlled Demolition At The WTC