Originally Posted by
Itinerant one
RN is for all premier levels while R is non premier. So RN availability should always be equal to or greater than R.
That's not really accurate. Premier instrument upgrades will almost always book into R. I don't recall ever booking into RN. It's basically a meaningless fare code at this time.
Contrast this with I/IN, where premiers specifically do book into IN.
Agree with
kb1992 that ON is typically greater than O, just as R typically greater than I.