The section of the Pentagon hit was reported to consist mainly of new, unoccupied offices. Barbara K. Olson had called her husband, Solicitor General [Theodore Olson]? at the Justice Department at 9:25 from the plane to tell him about the hijacking and to report that the passengers and pilots were held in the back of the plane.
See September 11, 2001 Terrorist Attack/Plane casualties for the flight manifest.