Re: who makes the best LONG gun cases for travel
+1 on the missile case. Mine ran about $175 delivered, and has worked out extremely well. They're built to transport a <span style="font-weight: bold">ROCKET WITH EXPLOSIVES</span> around the world, so they're definitely sufficient to protect a rifle. Or two. Or half a dozen. There's enough room in one to seriously store 5-6 carbines and about as many handguns, if you do some cutting of the foam and add storage into the lid. $30 at Home Depot allowed me make it mobile using 1/2" steel rod and some lawnmower wheels on one end (threaded through one of the stiffening brackets).
As far as the airport goes, your best solution would be to spray paint it in non-threatening colors, maybe stick a few Hello Kitty stickers on the side, or a peace symbol or two...much less likely to induce screaming and panic at the check-in desk one would suppose.