I find it easier not to wear a Sgian dubh in public, unless I am going to a formal occasion. In the USA I always remove my kilt pin and put it in the sporran before sending it through the x-ray. I also use sporran hangers when travelling as it makes it easier to get the belt and sporran off for security.

Because of my ankle replacement, I am always diverted to full inspection and have never had trouble wearing a kilt. They just make you stand with one leg forward when they run the wand down your legs.

Brian