Security checkpoints weren’t crowded before 9/11 because it didn’t take 15 minutes to get through security. I guess this is becoming lost ancient history. There was no ID check. There wasn’t even a boarding pass check — you routinely accompanied departing friends to their gate to see them off. There was none of this shoes off, no liquids, laptop out of the bag, just an x-ray and a metal detector.
The threat model before 9/11 was hijacking, not suicide bombers.
The threat model before 9/11 was hijacking, not suicide bombers.