Always difficult, if not impossible, in my experience. Often it is hard to even purchase a full-fare business class ticket. On some flights that I am looking at for later this month, the flights are completely sold out (business & economy). I guess that doesn't leave much for the frequent flyer redemptions. I think that South America is one continent where one-world is very underepresented - I think there are only 5 one-world flights per week to South America (LAN SYD-AKL-SCL). I'd be interested in hearing anyones suggestions as well.