Flew to Fukuoka today via Seoul. First leg on UA Polaris, second leg on KE Prestige/business, 2 separate awards. Asked the check in desk at SFO if it was possible to interline bag to KE so I wouldn't have to do customs in Korea. Surprisingly agent was very friendly about it and said no guarantees but let's give it a try. Had to provide PNR, origin/destination, flight number and booking class. Oddly, the KE PNR wouldn't work; he could only find the reservation from the DL PNR. Took him about 10 minutes but he was able to find the reservation and link them to reprint the bag tag to Fukuoka. Not sure if exception was made because of flying in Polaris but was pleasantly surprised and my bag made it just fine to the final destination.