Originally Posted by
BH62
Betraying my ignorance of the ins & outs of fare buckets, if a flight shows the availability of award tix, is it a logical "impossibility" that there are no "R" upgrades? Seems that a paid (say, V or W) fare supported with a GPU would trump the relative value of an award? And where would miles+copay upgrades fit into the hierarchy?
While there is probably some background linkage, it possible to have saver award inventory and there not be upgrade space and the reverse has also been seen. Mileage upgrades are the same inventory as RPU/GPU inventory.
X,XN is economy saver inventory and would be very different from R. Se the above referenced thread for more.