should be but do we really know if it is or not? And like Armed East Sider said why is there only a single hole in the Pentagon and no visual damage from where the wings would have hit?
If you avoid the conspiracy sites, listen to the actual testimonies of the people there, and there were plenty, you can find pictures that show where the wings hit and where people saw the plane, not missile. The conspiracy sites only show you the pictures where the smoke covers that part of the building and avoids the witnesses that saw the plane.