Percentage of Americans: 41%
Who believes it: Morgan Reynolds, chief economist under Bush adminstration; David Shayler, well-known British journalist

From ridiculous anti-Semitic theories to government insider allegations, there are a plethora of 9/11 conspiracy theories out there that make us ashamed of our fellow Americans. But one of the craziest would have to be the no-planes theory. In this conspiracy, it's argued that no planes were used during the attacks. Makes no sense, right? Well, according to Morgan Reynolds, chief economist during the Bush administration, it does. According to his theory, no planes or hijackers were used during the attacks because it would have been physically impossible for the planes to have penetrated the steel frames of the towers. So if those things that crashed into the towers, weren't planes—what were they? Missiles surrounded by holograms made to look like planes. Oh, of course.