I had a baby taylor for that, and it was nice although it's not quite full size.

I know you said acoustic, but just in case it helps you or anyone out there, my MusicMan Axis fits in the overheads in its case.... Although I've also never had a problem with my guitars in with luggage - the airlines are very understanding in my experience if you give them some warning and smile a bit... :)

Although they do always try to sell you another seat first...