It is just like any other luggage. You can buy fish boxes from the local stores in AK (styrofoam with cardboard shell). The fish will stay frozen for over a day. I flew from AK to Seattle, to Phoenix, stayed the night, then flew to Pittsburgh and it was fine.

Well, it would have been fine if the stupid TSA idiots had left it alone. They decided to open the boxes and inspect them, sealed the exterior cardboard box, but didn't close the styrofoam. Thus it looked like it was ok, but it was letting heat get in and almost thawed the fish. Keep an eye open for idiots with whatever method you use.