The captain of an aircraft flying an international flight is required to have a Restricted Radiotelephone Operator Permit. How do you get one?
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.