I've had a Ferro/Mg rod covered with a section of heat shrink on my key ring EDC for several years including 250,000+ miles of commercial flying over the past several years (ugh). Although I've had several "interesting" conversations with a/p security over various items, I have never had any problem. My guess is none of them know what it is, but figure it isn't threatening (looks like a 2.5 inch long plastic rod with the tube on it).