I just wondered if I were to book, say, an AA flight operated by Cathay in Business Class, could I then use miles to upgrade it to F? I realize that, if possible, it would be subject to availability, but my experience with an Alaska codeshare was that it had only the AA name on the reservation. I could not check in online, did not get priority boarding, and had no upgrade ability via coupons.

So, I just wondered if the same was true of all codeshares, and whether you are unable to use miles to upgrade if you are flying on an AA Codeshare?