On a fundamental level though, there’s a certain healthiness to maintaining the outlook that we are an overmanaged and underempowered society. Given that and the level of secrecy in said management, it’s no wonder conspiracy rumors thrive. The key is to get people to think it all the way through instead of stopping at the dramatic details. I think we live in danger of conspiracies far too public and in our face to make hay about secret operations.

The structural steel did not have to melt to bring down the towers. It only needed to reach the critical temperature where it effectively loses it’s load bearing ability. For the steel in the WTC this was about 1000F (540C). IIRC, even the 911-truth folks allow 800F to 1500F for the fires. Because ordinary office fires can reach this temperature even without kerosene as an accellerant, steel columns have to be insulated. In the case of the towers both abestos and another type of insulation (the name escapes me) were used and both were rated to provide four hours protection. However, this assumes the insulation was intact.

Given the design of the building, the outer aluminum supports would have offered little resistance to the plane. It is reasonable to accept that there was sufficent energy in the intitial impact to blow away a significant amount of the insulation on inner columns allowing the steel to be directly affected by the fire. I don’t know of way to prove it (tho simulations show it happening that way) but, if that is what actually happened and the fire directly affected the steel, the amazing thing is the buildings stayed up as long as they did.

The collapse of towers one and two were top to bottom. This is not typical of a controlled demolition as the 911-truth folks try to claim. A simplified version of blowing a tall building is: The building is rigged so the first set of charges cut support to the outer wall which then try to collapse inward. Then charges cut support at the base causing the core to try and topple but the inward falling walls constrain it. The result is the building collapses from the bottom up onto it’s own foot print. The towers all collapsed straight down but this the only similarity I see to commercial demolitions.

The collapse of WTC-7 is often presented and being impossible. Since it was closer to a ground up collapse it does more closely resembles a controlled demolition. The usual argument is that the fire was not extensive enough to damage the structure enough to cause a collapse. However, if you look carefully you will notice that the 911-truth folks only show you images of the North and East side of the tower. Find an image of the South side and you will see at least 20 floors of the building were fully involved before the collapse. The fire was far more extensive than the 911-truth folks would like you to believe.