Originally Posted by
jsloan
I'm not sure that UA is offering the discounted B fares internationally, but I agree that if one were to try this -- which I still don't recommend -- the B would be the first fare I'd look at, especially if OP is connecting, as the ability to confirm an upgrade instantly on the connecting flight, or to wait for PN rather than PZ, may make a material difference there.
Curious why you are suggesting to look at B first? Aren't R and A usually a lot less than B? Notwithstanding the higher UG probability, the PE fare also translate to B domestically and (should) carry the "instant PN upgrade" as well. Perhaps there is no PE on this route...