This hasn’t been announced officially, but Northwest Airlines employees are reporting that DL/NW will begin their reciprocal mileage agreement beginning April 1. Similar discussion on this topic is occurring in the
Northwest Airlines forum . It’s being reported there that the reciprocal lounge agreement will begin April 1 as well, but I haven’t heard any further information on that, nor have I heard whether or not DL/CO agreement will begin that date as well. The codeshare between DL/NW will NOT begin April 1.