The notion that the WTC towers collapsed because fire weakened the steel is laughable.
The fact that other steel-framed, steel-cored buildings have suffered much longer burning, much larger in extent and, demonstrably, hotter
fires, and yet never collapsed, shows how difficult it is in practice to bring down one of these buildings from fire.
Apparently, these buildings are robust structures, highly over-built to handle heavy wind loads; and it seems you would need to heat a large volume of steel, uniformly, over a wide cross-sectional area of the structure, to even have a chance of making one collapse in the neat, symmetrical manner witnessed (to the extent it is even, theoretically, possible to do this without resorting to explosives in the first place).
The easiest way to see that these buildings were rigged for demolition is to start by considering the fact that, between the time Flt. 175 hit WTC2 and the time the building collapsed, only 56 minutes had elapsed. And 56 minutes, simply, isn't enough time to develop a fire hot enough, nor large enough in extent, to even have a remote chance of getting enough steel hot enough to be a factor.
Say, for the sake of argument, that you’re concerned with one floor of the building. Assuming that you have an unlimited supply of readily combustible fuel available (which is, obviously, not true, but let's be generous), and there is no heat loss by convection, conduction or radiation (another ridiculous assumption, but let's give the shills every advantage).
Now, the rate at which the temperature rises on that floor will be determined by the composite thermal mass of the building materials associated with that floor, and the rate at which you can bring in oxygen to burn the fuel. Assuming, say, about 5E5 kg of steel, and about 1.4E6 kg of concrete, per floor (taking internet based numbers at face value), with specific heats of about 450 and 3300 J/kg*C, respectively, simple algebra shows that you would have to release about 3.27E12 Joules of energy to uniformly bring the temperature from ambient up to, say, 700 degrees C (starting to get into the interesting range, but probably still not high enough to cause a collapse).
That's right, in order to bring the temperature of one floor of a WTC tower from 25 to 700 degrees centigrade, uniformly, in a short 56-minute time frame, you would have to supply about 600,000 cubic feet of air per minute...for each of those 56 minutes. And that’s a ridiculously high number. And even if you did find a way to create such blast furnace like conditions, the fact of the matter is that you would convect a significant portion of the heat away, just like what happens in a fireplace; in order to let fresh air in, you have to let the heated, oxygen-depleted air escape.
If you were lucky, and the process was, say, 50% efficient (meaning the airflow only carried away half your heat), you would need to double everything, which would mean burning 60,000 gallons of jet fuel in 56 minutes, while feeding the fire with over one million cubic feet of air per minute.
By way of the above numbers, the absurdity of the "official" version of events is laid bare for all to see.