Now, let's see...in order to pull off the magic of technologically-impossible remote-controlled airplanes, you'd need massive amounts of cash. Therefore: Bill Gates
You'd need someone with no conscience. So, Ted Bundy.
You would need an intellectually brilliant polymath who was an expert in all sorts of fields. So, that could be Freeman Dyson.
Put them all together, and you have the only possible explanation for 9-11.
Dr. Evil.