[The Penguin]

It's not exactly a credible theory when you actually look into it. It may be widespread in the conspiracy world but only because people like to claim the wackiest theory possible and the US government is a popular target.

I'm not sure what proportion of people genuinely believe that Bush, Rumsfeld, Cheney and co were all in the oval office and decided "let's fly some planes into the trade centre and kill thousands of americans and while we're at it let's hit the pentagon too just so it looks like it wasn't us".