Hey,

Acutally, the answer to your question is yes!

You can REQUEST an upgrade, but you might not get anywhere with it. I got lucky a couple times and found a gate agent who read the rules and determined that Delta GMs could get upgraded. I IMMEDIATLEY had him upgrade me on several NW segments. (which he did)

Every other NW agent read the rules and told me that it wouldn't work.

One funny thing, though, is that I had trouble getting the NW upgraded segments to post. In almost every situation, I had to fax the boarding pass to Delta. I don't know what the agent had to do, but it must have been some sort of override).