Everyone makes mistakes.
1 person out of 100,000 flyers making a mistake is a very small fraction.
The psychological reasons can be very simple. Someone in the household places the gun in a carry-on, because they believe that is where it is supposed to be.
It is down in bottom, perhaps covered by other material. The person who uses the carry-on, checks quickly, but does not see it, or they are in the process of checking when they are distracted by an emergency, such as a child coming to them with a cut finger. Their mind says they checked, but they did not.
It is amazing how Murphy can trip people up.
No one is perfect, except for people on the Internet.
As always,
Have I got a story.
Going thru a bag check at the Wailing Wall
in Jerusalem they pulled out a triple edged nylon Spike about 10 “ long 😳!!!
Yuppers...forgot I had it. Inspector asked me what it was and I Shrugged ‘Letter Openener’ and ignored him. He put it Back.
I figured I got it That far might as well
Take it back to Indianapolis.
That was 1995 IIRC when it was Quiet there