I'm not sure if you mean formal gown or wedding gown, but this issue is part of what kept me from having a true destination wedding.
And since I've had time to think about the issue of poofy gowns and wrinkles and whatnot, I would say to just allow yourself time to have it unwrinkled. If it's a normal gown, have it drycleaned or get a steamer or bring a steamer. If it's a wedding gown and you think it'll survive, again, use the steamer (my 100% silk gown was fine with a steamer held several inches away, even though it's not really recommended but we got brave and tried it...but it had no beading on the fabric of the dress), or there's a wedding gown place in Orlando that helps brides out with this sort of thing and will de-wrinkle it (check out the weddings forum for that info). If, by chance, you're bringing it for a cruise, think about using their services once on board.
Checking it or carrying it on, you're going to be dealing with wrinkles. Taking it in the car caused wrinkles (hence the need for a steamer) in my case, so I didn't escape the problem, LOL.
And if you choose to put it in the overhead, wait until there is a base of luggage in the overhead then put the gown on top of the bags. If you put it in the overhead bin before there is luggage you are going to serious peeve people. Like the people who put their coats in the bins before luggage goes up there. Put clothing on TOP of bags, not in place of it.