This theory was floating round the internet a couple of years ago when a French website was making similar claims.
At the time, I found it all highly convincing, and I'm sure there is still much we will never know about 9/11.
But I can't really believe that with hundreds of film crews, journalists and photographers around at the time, that what happened to the Pentagon isn't as the US Government says it is.
It's a good little film you linked to, though. And the evidence is still very persuasive!