I fly always with my mandolin and am allowed to carry it on....perhaps you have the look of a homicidal maniac about you? Please don't take offense..that last bit was just a joke. As I fly trans-atlantic all the time....several times per year....I have come to know that there is also the possibility of having it hand carried aboard cargo....which you only need ask....OR...there are storage areas in passenger that airport personnel can also place an instrument. Be firm....and pleasant.