Originally Posted by emma dog
DL refused to upgrade me despite the fact that F from ATL-SEA was >50% empty because of "rules." It wasn't due to lack of effort on my part, either... similar to your story.
I'm interested in the idea that an airline won't upgrade you (AA in OPs case and DP here) when a ticket has been endorsed over to them. Don't the collect a full Y fare from UA in this case? I'd think that they would be happy to let you use your DL or AA miles. I'm curious what UA does in a similar situation. For some reason I think that I did this years ago on US with a ticket endorsed over from UA, but can't really remember.