A non-conspiracy theory about 9/11 that deserves discussion:

[hedgehog]

In the aluminum industry, the biggest fear is mixing liquid aluminum and water. First, you get a steam explosion, spraying droplets of molten aluminum everywhere. Then, the aluminum droplets burn. It takes a lot of energy to separate aluminum from raw minerals; when aluminum burns all that energy is released.

Here's what happened at one aluminum plant in China:

http://shanghaiscrap.com/2007/08/shandong-to-dead-workers-dont-blame-us/

So, here is a speculation floating around the aluminum industry:

1. The fires at the World Trade Center may not have been hot enough to melt steel, but they were certainly hot enough to melt aluminum.

2. The planes that hit the towers were made from tons of aluminum and titanium.

3. So, liquid aluminum and titanium flowed down inside the buildings until it met water from fire sprinklers, then the mix exploded.

Simensen believes that it is overwhelmingly likely that the two aircraft were trapped inside an insulating layer of building debris within the skyscrapers. This leads him to believe that it was the aircraft hulls rather than the buildings themselves that absorbed most of the heat from the burning aircraft fuel.
The SINTEF scientist believes that the heat melted the aluminium of the aircraft hulls, and the core of his theory is that molten aluminium then found its way downwards within the buildings through staircases and gaps in the floor -- and that the flowing aluminium underwent a chemical reaction with water from the sprinklers in the floors below.
"Both scientific experiments and 250 reported disasters suffered by the aluminium industry have shown that the combination of molten aluminium and water releases enormous explosions," says Simensen.


http://www.sciencedaily.com/releases/2011/09/110921074747.htm