I have a question regarding crediting CO travel in a partner's frequent flyer program (Delta, in this case, but the issue applies to any partner.) Having already requalified for 2008 plat, I am contemplating using my future CO/NW travel to improve upon my lowly DL silver status. Is it possible to use my CO FF# to secure an upgrade, and then just prior to departure, ask the gate agent to replace it with my DL FF#? Will the system sense that I am not elite, and take away my upgrade? The CO reps who I’ve asked have so far been clueless, and I haven’t had the balls to try this at the airport for fear of being shuffled back to coach.