IMO, one should keep their firearm luggage and their air travel luggage completely separate. I don't take my range bag on the plane, I don't take my good luggage to the range. That prevents issues like a forgotten round/gun/etc. from getting me tossed in the clink.
If one absolutely MUST cross pollinate, then it's on that person to properly sanitize the bag from any kind of gun or ammo. If that isn't done, well, my compassion is pretty limited. Should it be a life-ruining error? That's up for discussion, but I could see people trying to deliberately sneak guns onto the plane and just try to shrug it off as an error to avoid the legal consequences of the attempt.