Check American's website for award availability in the Saver level. If it's available you should be able to book it with BA Avios for 25k round trip . Otherwise check United's website and see if they have Saver level availability. You can book with Singapore miles for 35k round trip. Another option is to check Delta for the lowest level availability and book with Korean miles for 25k round trip. Also you can mix and match with one ways depending on availability.