Section 403 of the Act and this final rule provide that carriers are required to allow passengers to stow their musical instruments in an approved stowage area in the cabin only if at the time the passenger boards the aircraft such stowage space is available. With the exception of certain disability assistance devices, overhead bins or under seat stowage space is available to all passengers and crew members for their carry-on baggage on a “first come, first served” basis. Accordingly, carriers are not required to remove other passengers' or crew members' carry-on baggage that is already stowed in order to make space for a musical instrument. However, this also means carriers are not allowed to require a passenger to remove his or her musical instrument that is already safely stowed (e.g., in the overhead bin) to make room for carry-on baggage of other passengers who boarded the aircraft later than the passenger with the musical instrument. This is true even if the space taken by the musical instrument could accommodate one or more other carry-on items.