Originally Posted by
jsloan
UA should be recalculating the price, but I guess I’m not shocked if they’re not. However, if the second leg is a partner leg — which it sounds like it is in this situation — it’s possible that the change will error out if there’s not additional inventory on the target flight.
That has not been the case in the times that I’ve done this (I've only ever done this with ANA, EVA, Thai, and Asiana, but so far it’s been 100% success rate). Again, there is no barrier to testing this out now so if you’re skeptical, I’d encourage you to try it for yourself. The worst that could happen is you cancel the entire itinerary and get all your miles back, best case, you save 10%+ on your next *A award.