I've never flown while kilted, but I've been to many many concert security checkpoints and was surprized as to how many of the security guards simply let me pass without any screening whatsoever!
The usual drill is to get in line, go through a metal detector and/or get "patted down".
What usually happens with me is that when it's my turn to get patted down the security guy just looks at me with a puzzled look like he's thinking "Ummmmm, what do I do now?" before waving me on.
Wear your kilt proudly, but carry a big stick
Bookmarks