I flew United and American recently and in both instances was required to check my banjo in as "luggage" rather than as "carry-on." Thus, I would not count on being permitted to carry any instrument on, but you might be lucky. If the instrument is loaded as checked luggage, you also can't count on it being hand-carried to the special handling area at the end of your flight. Mine was dealt with fine until my final stop back home where it catapulted from the luggage chute, flipped several times in the air, and landed in my arms. Somewhere in the process the case hinges gave out, which was O.K. because I also strapped the case. If you care about your instrument, I've concluded that air travel is currently a stressful proposition. Good luck!