Originally Posted by
Mike Jacoubowsky
Yep. The UA booking engine doesn't work right if you ask it to give you a refundable fare *and* a miles-based upgrade. Unfortunately, the reasons I can't figure out, the miles-based upgrade eligibility may fizzle when you go for the refundable fare. That I don't get.
The availability of RN space does not vary based on fare BUT using multiple search options (such as a fare class or refundablity and for a mileage upgrade) is notoriously flaky. Look for RN using expert mode and than book the flight doing the upgrade afterwards. If for some reason the upgrade disappears in that short window, you can cancel and fully refund in 24 hours. Unfortunately the Advance Search options do not play well together.