I posed a similar question--pilots from America and other spots, but I got the impression that the Germans were less inclined to accept help from outside the Fatherland. In fact, I don't recall hearing about any outside help. One odd item having to do with Germans and Irishmen and the war swirls around the writer Erskine Childers. I've read that Childers ran German arms to the Republicans then turned around and flew for the RNAS. Not the first character in the war to take opportunities as they presented themselves.