NW and KLM for years operated a somewhat different arrangement on their trans-Atlantic routes, rsulting fromt heir much deeper joint venture. My understanding is that they pooled revenue from all sales of transatlantic seats whetehr on a KL or NW flight #), and split the profits according to a pre-determined. One advantage was that any seat on an aircraft could be sold by either KL or NW, whereas in the more traditional "hard block" code share AA may have sold its allotment (in a particular fare class or entirely), whereas the operating airline may still have large numbers of seats open. This leads to the problems often noted on this board code-share flights ticketed on the non-operating carrier often appearing to eb significantly more expensive, not available for award travel, etc.