This is a domestic flight. I would assume that jeans in first would be o.k. because Delta is saying that NW will follow Delta's relaxed dress code policy.However. I may dress in business casual to be on the safe side.I really don't care which cabin I am assigned, I just want to get ON and the opportunity looks better in first. Has anybody from DL actually non-reved recently on a NW(not code share) flight?