The SKB ATA double rifle case offers good protection, but it's big. Do a google search to see one. Beware of aluminum cases with plastic structural corners, they won't handle a drop.
Americase is good, but they're heavier and more expensive.
I have a Pelicin case for two rifles. It is very solid and have flown with it quite allot. I think it was over $200. but worth it. The case has two locks that are called TSA, so I guess they have keys for it also. It will easly hold two scoped full size rifles. It has wheels on one end so you can pull it once you are in a airport.
Chop