I haven't, yet, but the last trip out to SW Colorado, I asked the lady at check-in because I was somewhat confused by the hard-cased requirement. Either your bag must be hard-shelled and locked or you can put a hard case inside your baggage. It has to be separately locked... NON-TSA lock, by the way... only you have the key or combination.
I got a metal mini-safe and have some pix I'll post. I plan to carry my PM45 and probably 4 boxes of FMJ... maybe less... we're allowed to carry up to 11 pounds of ammo in its original packaging or in magazines enclosed in a case... bullets not visible. The ammo can't be in the same case as the gun, but can be in the same piece of baggage. The gun should be unloaded and be prepared to show this to the check-in clerk, before locking up the gun's case. Don't arrive too late, in case there's a delay getting your bag checked. There is a great need for tact... don't say loudly, "I have a gun". You might not make your flight on time.
There's a chance you'll have to open and show that the gun is unloaded when the baggage handlers x-ray and see a gun. So leave your cell number on the bag and be ready for a call. You would think they could tell with an x-ray that there's no bullet in the gun.
These safes run about $20 to $35, depending on what locking system and where you purchase the Travel Safe. One full-sized 1911 will fit... my S&W 645 5" fit, OR, any TWO Kahrs will fit... just leave room for the locking mechanism... where I put a piece of yellow PostIT to show the space needed. Note the inexpensive, but very functional bike tube (1.75") grip covers. They work and don't detract from the looks.
I plan on using the included cable to lock the safe to the luggage bag's steel post spine. I might take the barrel out and put the trigger lock on it as well. I have some of those water-tight plastic cases like Pelican or others sell, that I'll put the ammo in, along with maybe a few loaded mags in their holders.
Check your airlines requirements and the relevant TSA or Federal website and the rules, etc. there. Some others who HAVE done this will probably be better able to answer questions.
USAF Retired '88, NRA Life Member. Wife USAF Retired '96 Avatar:Wynn re-enlists his wife Desiree, circa 1988 Loring AFB, ME. 42nd BMW, Heavy (SAC) B-52G's
Frédéric Bastiat’s essay, The Law: http://mises.org/books/thelaw.pdf
Thomas Jefferson said
“A government big enough to give you everything you want, is strong enough to take everything you have.”
and "Peace is that brief glorious moment in history when everybody stands around reloading".