Originally Posted by schley

If you have any elite status then you can use the RN availability, but R is for non elite and all passengers. The N basically signifies elite availability for the upgrades. At this time there aren't any reports I'm aware of that R/RN are different. I believe the UA rep on FT confirmed that they aren't using RN yet or at least differentiating that bucket from R, but I maybe wrong.

When looking for award buckets the N has more meaning.

ON-first class in 3 cabin, IN-business class in 3 cabin or first class in 2 cabin for plat/1k/gs. All other levels of status only can pick the O/I availability that is available for all passengers. XN is for all elites in economy.