FCC License - Element 6

You need a commercial radio operator license to operate the following:

Ship radio stations if:
the vessel carries more than six passengers for hire; or
the radio operates on medium frequencies (MF) or high frequencies (HF); or
the ship sails to foreign ports; or
the ship station transmits radiotelegraphy; or
the ship is larger than 300 gross tons and is required by law to carry a radio station for safety purposes.
Aircraft radio stations, except those which operate only on very high frequencies (VHF) and do not make foreign flights.