Tracing the Pre-9/11 Events: Weaponry and Preparations

In August 2001, the Federal Aviation Administration’s intelligence office issued a warning to airlines. The circular, titled Disguised Weapons (IN-2001-12), highlighted the risk of terrorists using modified everyday objects as weapons for hijacking aircraft.

This advisory did not impact airport security significantly. The perpetrators of the 9/11 attacks used knives and razors, which were allowed on planes at that time. Records from doomed flights show that these tools were used to subdue resisting passengers and crew, resulting in stabbings and cuts.

Khalid Sheikh Mohammed, a key planner of the attacks, began exploring ways to smuggle knives and razor blades onto flights in December 1999. His associate, Walid bin Attash, known as Khallad, carried a razor knife during a flight from Pakistan to Malaysia, testing security measures on U.S. flights to multiple destinations.

Khallad shared his findings with Khalid Sheikh Mohammed and Mohammed Atta. Atta, after meetings in Spain, returned to the United States on July 8, bringing two Victorinox Swiss Army knives he bought at Zurich airport.

Post-9/11 investigations by the FBI uncovered that terrorists on each hijacked flight had purchased at least seven knives. Marwan al-Shehhi, who piloted UA Flight 175, bought knives from a Florida Sports Authority store on August 13. Two of his associates acquired additional knives from a local Wal-Mart.

Nawaf al-Hazmi purchased a short-bladed multi-tool at a Target in Maryland on August 27. While financial records for UA Flight 93, which crashed in Pennsylvania, show no weapon purchases, the FBI retrieved 14 knives including box cutters from the site. None had blades exceeding 3.5 inches in length.

Ramzi Bin al-Shibh, later captured, informed interrogators of his discussions with Atta and others about executing the hijackings. The pilots reportedly faced no issues carrying box cutters on domestic test flights.

Newsweek is documenting the events leading to 9/11, reconstructing them day by day as they unfolded 20 years ago. Each day a piece of this chronology is published. On September 11, Newsweek will provide minute-by-minute live coverage of the events, starting at 4:45 a.m. EST on Twitter at @RoadTo911.