Fuel! Or the lack of it!

There’s apparently a freeware Ascension airport add-on:

https://forums.flightsimulator.com/t/freeware-missing-airports-st-helena-ascension-barra-kai-tak-hong-kong-tresco-gaza-vagar-faroes-thule/279666

No idea if it’s any good. Seems to be a work in progress, but as long as you can land, and take off again, it’ll get you across the Atlantic. Otherwise, your next option is probably via Fernando De Noronha (SBFN) .