The 9/11 truther conspiracy is well known, well debunked, and still widely believed by many. There are just as many theories regarding the hijacked Boeing 757 that attacked the Pentagon, mostly based on discrepancies between the sizes of the hole in the building exterior, the hole in the middle ring, and the plane’s wingspan. French author Thierry Meyssan, among others, insists the attack must have been a missile attack by the US military.
These theories suffer from a failure of imagination. Structural engineering professor Mete Sozen, a member of the American Society of Civil Engineers who went over the blast site, explained in Popular Mechanics: “A crashing jet doesn’t punch a cartoon-like outline of itself into a reinforced concrete building. In this case, one wing hit the ground; the other was sheared off by the force of the impact with the Pentagon’s load-bearing columns. [ . . . ] What was left of the plane flowed into the structure in a state closer to a liquid than a solid mass. If you expected the entire wing to cut into the building, it didn’t happen.”
Other questions revolved around the intact windows seen in photographs and the supposed lack of plane wreckage. For the former, it was because they were blast-resistant, designed to resist force significantly stronger than a hurricane. As for the wreckage, there are photos available. According to Allyn E. Kilsheimer, who arrived early at the scene: “It was absolutely a plane, and I’ll tell you why. I saw the marks of the plane wing on the face of the building. I picked up parts of the plane with the airline markings on them. I held in my hand the tail section of the plane, and I found the black box. I held parts of uniforms from crew members in my hands, including body parts. Okay?”
Several other claims have also been debunked. Security camera footage supposedly proves an object too small to be a 757 hit the building, but that was because the ultra-wide angle was designed to see as much of a vehicle driveway as possible—the image was not rectilinear and thus was distorted. A Dulles air traffic controller, Danielle O’Brien, said, “You don’t fly a 757 in that manner. It’s unsafe,” which was used by conspiracy theorists as proof of their claims. However, O’Brien continued, saying “It was never the intent of the hijacker to safely land American flight 77 anywhere.” Many have said the Pentagon’s missile defense system should have shot the plane down. No such defense system exists, and given that Ronald Reagan Washington National Airport is less than a mile away, one would be highly impractical anyway.