To The Contrary, Whatever Struck the Pentagon Was Likely a Boeing 757.

The core of the talk's argument in support of this conclusion is that the wings and rudder of a 757 would have left impressions in the Pentagon's facade, which are difficult to see in the available photographs, and that the starboard engine would have done more damage to the first-floor columns.

The argument about the damage to the first-floor columns may rest entirely on a misinterpretation of the photographs, described here

The argument about the lack of impressions of the wings and rudder is not as compelling as it might seem in light of the following facts.

• Details of the construction of the Pentagon's facade remain unclear. The portion of the facade that the plane hit had recently been upgraded to include steel- and Kevlar-reinforced walls and blast-resistant windows.
• The portions of a 757 that would not fit through the punctures in the first and second floor were the outermost and lightest portions of the plane's wings and tail, consisting approximately of the outermost 30 feet of the wings and rudder.
• There was damage to the facade beyond the 90-foot-wide expanse of breached walls, and that damage is arguably consistent with the impact of the outermost portions of the wings.

Even if one is convinced that the outermost and lightest portions of an intact 757 should have left obvious impact impressions in the facade, it does not follow that Whatever Struck the Pentagon Was Not a Boeing 757. For example, a scenario introduced by Eric Bart explains the lack of an impact impression without supposing that there was no 757 or that there was only an overflying 757 -- both suppositions contradicted by the eyewitness accounts. His suggestion that explosives planted in the plane destroyed the airframe at about the moment of impact accounts for the observation of an impact damage pattern not precisely matching the profile of a 757.