A great deal has been written about the damage to the Pentagon on 9/11. The focus of this discussion is on the mysterious, and officially unexplained, “C-Ring Exit Hole”. The C-ring exit hole is significant because it is not consistent with building damage from a Boeing 757 impact. The C-Ring exit hole carries a unique signature, which can only be explained by something other than a 757 impact. No explanation is offered for this hole in the Pentagon Building Performance Report http://fire.nist.gov/bfrlpubs/build03/PDF/b03017.pdf or the official 9-11 Commission Report.