Other mistake: On-board Flight 93, Mark Bingham's conversation with Tom Burnett about sports is repeated twice in two separate scenes. You can tell if you listen out for Bingham's line, "You take out all your aggression and all your, you know, all your shit for the day." The dialogue is heard in the background the first time around and then given more focus the second time. (00:46:49 - 00:55:35)
Other mistake: At New York ATC, the radar shows American Airlines Flight 11 disappearing over Manhattan, indicating that it has just crashed into the North Tower. This occurred at 8:46 a.m. Around a minute and a half later, Sgt. Jeremy Powell at NEADS directs the scrambling of fighter jets in search of American 11. He states that the time is "0846" (meaning 8:46) - should be 0847. (00:34:55 - 00:36:17)
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.