Probably late for this, but I travel with an old Suzuki Dreadnaught that I got at a yardsale for $25 in a gigbag with an extra long shoulderstrap--always as a carry-on--I had a hardshell case (tht cost more than the guitar!!)and used to check it, until I picked it up three days after I arrived in LA (!!!) and one of the sides of the case had been meticulously pried off--
I always carry it over my shoulder, tucked behind me when I board the plane, and generally, the flight attendents do not even notice it--
However, I just picked it up, about an hour ago, from the airport van shuttle office, because I left it in a van that brought me from the Baltimore airport--I thought my wife brought it into the house, she thought I did-it took a week to locate the driver--so no plan if fool proof--
The reason that a lot of the big rock stars play those injection molded plastic guitars that seem so loathsome to those of us who treasure vintage and handmade instruments, is that they sound and play reasonably well and yet can be replaced by an almost identical instrument almost anywhere, in case one is lost, stolen, destroyed etc.
Don't take your Martin to town, boys, leave your Martin at home!