+1,000,000. I've been checking almost daily on NRT-LAX for the past 5 months and no U inventory (what is needed to upgrade an M fare) has been available. I was able to upgrade the outbound months ago, but the return isn't panning out.

Just call the elite line, give them the dates of desired travel, say that you want to use a PMU, then ask if space is available. If not, ask for alternative dates. Good luck.