Musicians travelling by air have long struggled with figuring out how/if/when they will be allowed to bring their instrument in the cabin, rather than expose it to the not-so-tender mercies of baggage compartments and handlers. The US government recently passed this law creating uniform rules for allowing instruments into the passenger cabin:
Musical-Instruments-on-Aircraft-US-Law-2012
BUT… as of this date it is not actually in effect, because it set a deadline
Not later than 2 years after the date of enactment of this section, the Secretary shall issue final regulations to carry out subsection (a).
In the meantime, here are some ideas to help make your instrument-toting travel smoother: