I have to second vinnyc in this case: DL T class is usually cheaper than AF lowest booking class and yields 100 % miles. I did the same for my next trip to LAX next month, though only the return is on AF metal. I entered my seat preferences into DL's booking system and it showed up on checkmytrip.com with the confirmed check. By the way: the only way I could access AF's PNR was to enter my DL ticket number at airfrance.us.