Guns are easy, hard sided locking case. Do not use zip ties... some one tried this and was promptly told NO. My brothers and I always use soft sided cooler bags/totes and placed them in the checked bags. We have brought back birds, deer, and fish with no issues. Just freeze it completely if possible (freeze the fish 100%). If not, get it as cold as possible and wrap it in plastic, freezer paper, and then put each cut into ziplocks. Any leaks from the bag and they may toss it all. Also, put the cooler bags you are going to use in the freezer with the lid open, this helps a great deal to keep everything frozen or cold much longer. We can get a boned out whitetail doe in a 36 can tote. You are allowed to use dry ice too, something to keep in mind if need be.