Geeze, I had to go to Wikipedia to remember what our codeshare was called with KLM. Wings.

(Wikipedia) Also in 1993, Northwest began its strategic alliance with KLM, which was the largest airline partnership ever conceived at the time. This partnership eventually became the Wings Alliance. However, the alliance never grew beyond the two airlines, and is now obsolete from a passenger's perspective, because both airlines are part of the larger SkyTeam Alliance. (From a legal perspective, the Northwest/KLM alliance remains important: it has antitrust immunity, whereas the broader SkyTeam alliance merely has code-sharing privileges.)