Ummmm.... Not to be picky - but I'm going to be. It has been stated above a couple of times.

1. The impact of the aircraft damaged, but did not destroy either of the towers.

2. Thousands of gallons of jet fuel racing through the open galleries (what every office building in the US built after @ 1970 is, regardless of building code used), down elevator shafts and into open areas, when set alight will weaken, and in some cases melt, steel.

One of the chronologies of 9/11 I read recently was patched together from several sources. It seems that one of the chiefs told Guilliani about the same time as the second aircraft hit, that they were reasonably sure they could "save everybody below the fire". The first, partial, collapse of the first tower would have sent the weight of the debris onto the levels immediately beow the impact. The openings in the floor surface resulting from that would have allowed the burning fuel and debris to start working its way down.

The Empire State Building WOULD have been turned into rubble if hit by a modern aircraft. The Mitchell did damage the facade when it hit - the facade on the WTC was metal and glass - not enough to resist a jet aircraft travelling at speeds many times faster than a twin-engine B-25 could dream of going.

Regarding surrounding structural steel with masonry - this is a false argument. Cracks, fissures and holes in the masonry caused by the shock of the impact would have delayed the inevitable - at best by a few minutes.

To use masonry as a skin as the Empire State Building has - would be to build that high and not much higher. The mechanics involved would not work to allow the structures to get higher. Should office buildings be that tall? Well, either build up or out. Pick one.

There - that's my tuppence to this silly thread...

Pete