I always put a heavy plastic cable tie through the barrel and let the slide close with it sticking out the ejection port. TSA can see it's not loaded without racking the slide. Always, always, always check the baggage tag the ticket agent puts on your gun case (or the bag it's inside) to be sure it's the right one. One of those "nervous" agents sent my best shotgun and Glock to Canada, I went to Baltimore. Had H*** getting them back. Still believe the mixup was intentional.