I've always run away from codeshares because of uncertainty over fare code mapping and hence mileage accrual. I'm curious how others deal with this. I'm aware that in most cases alliance-coded non-alliance-operated flights don't earn miles. I also guess that alliance-coded alliance-operated flights in business and first will earn miles at the operating airline's business/first rate in your program; correct? Perhaps this is why there's not so much discussion on this; loads of you fly C and F . Which brings us on to the myriad of combinations for Y flyers. Now, that standard rule applies: you earn as per the operating airline's earnings in your program. The trouble is, the fare code on the codeshare ticket could map to any fare code as far as the operating airline is concerned, and I've never discovered a way of checking this up front, save to find someone who booked the exact same codeshare and fare: hard. Any advice?