That's a lot of "harmless" razors for one group of passengers.
EMPTY YOUR POCKETS means EMPTY YOUR POCKETS before going through the detector.
FWIW, air crew were murdered on the flights. If they didn't bring blades, they had to kill them some way (strangled?).
It's well documented that these dudes spent hours at the gym during their time in the US engaging in hand fight tactics, knife fighting etc.. We keep saying box cutters because that may be all we know but I'm betting that everyone of them had a knife on them. They're throat slitter people!!