My current experience with a banjo is that on United, international, I was told to load it as checked baggage and sign a waiver for damage. It was too large for cabin storage. When I arrived at my destination I found my banjo in a special baggage holding area, for fragile items but there was no assurance that that would happen and it is distressing if you're waiting around at the regular baggage delivery area and your instrument doesn't show up. My case hinges got trashed but since I had also belted the case, it was still intact. For my return trip I have substantially reinforced the case with new hinges and an additional belt. I also recommend tuning down the strings and stuffing all vacancies with socks and underwear. Good luck!