How about where both are available? In the case of X/XN, posters have indicated that there's still an apparent glitch in which XN inventory will be pulled for a PP/1K/GS with X still available. I have consistently experienced this as well.

OTOH, I just booked a domestic F award in which both I and IN were available. In this case, I inventory was used.

Anyone know why the discrepancy between how I/XN and X/XN behave for PP or higher where both of like kind are available?