Trivia: Families of the 40 passengers and crew members killed on United Flight 93 cooperated in the production, offering Greengrass detailed background about their loved ones, down to the clothes they wore, what reading materials or music they had with them and what sort of candy they might have snacked on aboard the plane.
Trivia: The FAA National Operations Manager, Ben Sliney, was played by himself. September 11/2001 was also his first day on the job.
Answer: At the time of the 9/11 incident, certain type utility or pocket knives like the ones the terrorists brought on board were not illegal. Airport screeners had more leeway then about what type of knives, tools, or other gadgets they allowed passengers to carry on board. Since then, the restrictions are far more stringent.
raywest ★
I can attest to this as my father traveled on aircraft with his pocket knife multiple times before 9/11. As long as it was under a few inches; it was more viewed as a tool than a threat to the aircraft.