There are in most Comonwealth and NATO forces slots for exchange aircrew to serve , {during my miss-spent youth I did in fact do such a tour} also in the past some of my age group did transfer to other Air Forces, but they were already experienced military aircrew. One of my close friends even got himself shot down during such service, after a short camping holiday he made it back in one piece however, Outside of this I think you are SOL.