Federal law prohibits any external markings or tags from being put on checked cases containing firearms.When I was living part time in TX and part time in NY I kept a couple guns in a safe in each state. that worked out well for me for the most part but one trip to NYI brought two guns on the plane and almost had them stolen.
They were legally checked in and tagged but someone broke the suit case lock expecting to find guns inside. But what they found inside was a very large sturdy case with locks that were a lot harder to break than regular suitcase locks. Trust me on this when I say gat a large box that is so big it can't be hidden under a coat and locks that would require bolt cutters or a hack saw to open. Putting the box inside a suitcase provides extra security.
Knowing this part of the law could have prevented this from happening and probably avoided the attempt at pilfering.