Crazy. If you get a permit do they not explicitly tell you carrying your gun across state lines may result in a felony? I'd think people would be wary of that. And also taking guns on a plane... to other countries.
Ya know, maybe it was one of those big backpacks and the gun was in an interior compartment and he just forgot about it. I know people that have camp knives and stuff in their bags and have accidentally carried them onto planes.