jackthehack said:
Not a single airline, but was operating under assumption that acoustic guitar would be in hard shell case; you CAN buy seat on most airlines for oddball delicate items you do not wish to check, have seen cellos/basses traveling this way. Don't know about using a gig bag, if for some reason you were NOT allowed to carry it on board, there is great potential for damage. The overhead bins in many aircraft are NOT long enough for a full size acoustic or electric guitar to fit into; due to location I typically fly 737s/MD-80s and there's no way on those....
While the TSA will let you through the security gates with an instrument, it is ultimately up to the airline and the specific flight crew to determine if your guitar will be allowed onboard. As more and more people bring larger carryon bags, I would be reluctant to try putting a guitar overhead. If they make you gate check your instrument and you only have a small gigbag, be prepared for damage. I used to hang my bass in the coat compartment, but more airlines are taking those out and replacing them with an extra row of seats. Don't count on the specific plane having a closet these days.
I bought a hardshell golf club case for my basses. A double gigbag, extra padding and spare gear fits in it just fine. I always check my bass these days and have yet to have a problem. In many cases, the airlines will run the case through their oversize luggage area and not down the general luggage ramps. I have yet to be charged extra for the golf club case either. I know several guys that use SKB keyboard cases and put their guitars inside a gigbag inside the hard case. Much easier to carry than those heavy ANVIL cases.
Here's what the TSA has to say on instruments:
http://www.tsa.gov/travelers/airtravel/assistant/editorial_1235.shtm