A mysterious helicopter was seen flying near the Pentagon in the minutes before the attack there on September 11, 2001. Several witnesses have described seeing the helicopter, which circled the Pentagon and then apparently landed for a brief period on the helipad, near where the building was subsequently hit. It then flew off very shortly before the attack took place. And yet there has never been any public acknowledgement of this incident, or any official explanation of what the helicopter was doing at the Pentagon at that time.

While interviewing one of the witnesses to the incident, however, a Navy historian revealed that the helicopter belonged to the United States Park Police, and, the historian said, had been instructed to intercept the aircraft that was on a crash-course for the Pentagon.