I'm glad I found this thread. Asking for some advice from all you seasoned pros, as I only fly domestically. I'm trying to determine best way to fly to LHR from SEA in end of Jan 2019. There are great fares right now for Y class. IcelandAir is $350 or BA is $500. I won't get miles with IA, but will get minimal (25%?) with BA. I've never flown either. Opinions if you were in my position.