Four of the five hijackers who crashed an airliner into the Pentagon on 11 September 2001, were pulled aside for additional security checks before they boarded the plane but were then allowed to take their seats, video footage reveals.
Surveillance footage taken at Washington's Dulles airport shows the four receiving additional scrutiny after setting off metal detectors.
The video, obtained by several media organisations from a law firm representing the families of those who died, shows an airport screener hand-checking the hand-luggage of one hijacker, Nawaf al-Hazmi, for traces of explosives before letting him continue on to American Airlines Flight 77. He was accompanied by his brother, Salem, a fellow hijacker.
A total of 59 passengers and 125 people in the Pentagon were killed in the attack.
An independent commission investigating the 11 September attacks is due to issue its final report today. The report is expected to highlight a series of institutional failures within the government and the intelligence agencies.