I've just been taking First-class passenger missions from the Sol system.
Mostly because the pay is good (between 500k and 1mil for transport missions, generally between 1mil and 5mil for sightseeing missions...) But also every minor faction is Fed aligned, so while not meaning to I've gotten a rank and a half or so.
Mostly I picked Sol because I'm allied with every faction, so they give me great mission contracts xD
Being able to carry 42 first-class passengers doesn't hurt, though...maybe one day I'll fly a Beluga for a few seconds (and then decide it's expensive and an easy target for pirates...)