I called UA this morning to try and find flights that could be upgraded at booking for an upcoming TPAC. The agent was able to find a couple of segments with space, but when I use expert mode on UA, I can find more segments that show R1/RN1 or maybe even R4/RN4... these are segments that the agent didn't mention were available. I was under the impression that a non-zero R number almost always meant you could upgrade-at-booking... is this a reasonable assumption?

I have to book all my travel via the corporate agency, so I have to mostly do all the legwork and have something I'm very confident in before I call and get it booked ;-S