Originally Posted by
jsloan
Anecdotally, they appear to be creeping in internationally as well. There's less of a benefit for a Premier to booking long-haul B fares, since the instant upgrade does not apply on long-haul routes, but it would still move somebody up near the top within their status level within the Economy cabin. It might also be the cheapest way to reduce a flight to 40 PlusPoints for upgrades instead of 80.
My hypothesis is that the reports we've seen have been tied to the YBM upgrade not working properly and/or PN (or PZ, for non-1K) space not being available. I don't think UA's IT is capable of doing anything beyond looking at the inventory class to make these determinations.
B will also save you the $ for the copay if upgrading with miles. Depending on the itinerary the saved copay $ can be greater than the difference between B and lower fare buckets.