I've only done one dive trip on a plane, but here's my 2 cents. I agree with everyone else, that you probably can't pack 2 sets of gear in one bag, especially if you have thicker suits. I used a medium/large size regular roller suit case, w/ a TSA lock and put in my suit, hood, fins, BP&W, back up lights, mask, weight belt (no weights), small cheap camera, and miscellaneous stuff (towel, log book, etc.). The suitcase was stuffed full and was pretty heavy.
For my carry-on, I have a Stahlsac bag that functions as both a padded regulator bag and also has an attached large mesh bag that stuffs into a zippered pouch in the outside of the regulator bag. I put my reg, SPG, octo in the regulator bag.
I put this ~1' round bag into a cheap Walmart small duffle that held my other carry on goodies (books, mags, snacks).
When I got to the hotel, I unpacked the suitcase, unstuffed the large mesh dive bag from the reg pocket, and packed the suitcase stuff into the mesh bag. The regulator stays in it's own pocket which flips into the end of the mesh bag, making a neat convenient way to carry gear.
It worked great, as you really need some type of mesh bag to carry on a boat or put in the trunk of a car as you get to the dive site. I don't know the model # of the bag, but it was ~$30 at my LDS. It's a grey color, about 1' in diameter when folded and stuffed, but opens up to about 3' long with a nylon fabric bottom and black mesh top.
John