Same as the above, unless you are at a hunter friendly lodge or hotel:
1. Break it down and carry inside your luggage. Get a rolling duffel with a zipper compartment below which holds a slim alumimun gun case.
2. Secure the hard case with a bicycle cable lock.
3. Buy a contruction site gang box, like electricians use to transport tools and lock them up on a job site, and put it into the back of your SUV.
4. Long ago, I had a steel box made for my vehicle or hunting cabin, which has a recess for the padlock, so no cutters can reach it. It is painted a blue/gray, like the interior carpet, and sits below the window line. It has 4 holes in the bottom so that I can bolt it to a floor in a closet.
5. Also long ago, I built a two piece cabinet which fits into a pickup bed with camper cover or a big SUV. They create a false floor in the vehicle. The front section has a trap door. The back section has a drawer which hold long guns and ammunition, and slides out over the tail gate. There are companies which sell these now, like Truck Vault.
I travel all over the USA with firearms and fishing tackle, and never had a problem.