47 CFR 87.87 requires the captain of a US registered aircraft to have their Restricted Radiotelephone Operator Permit (RP) unless it is a domestic flight.
How do you go about getting one? I used the FCC's website a long time ago and remember that it is terribly confusing. A great answer would include step-by-step directions for those that haven't had to do it yet!
You have to use the remarkably obtuse FCC Universal Licensing System if you want to request a license online. You'll specifically need FCC Form 605, the apparently very-accurately-named "Quick-Form Application for Authorization in the Ship, Aircraft, Amateur, Restricted and Commercial Operator, and General Mobile Radio Services".
From there, you're on your own, I'm afraid. I applied for mine years ago and it looked identical.
Do note that this is essentially a fee on operators who fly internationally, as there's no exam to complete and no proof of eligibility to provide. You simply request the license and pay the application costs. It's a bit silly.
