One of the issues that had to be ironed out is how each airline handles the attribution of frequent flyer credit through various fare classes. For instance, when I fly Continental, I sometimes get credit for a 'segment' rather than my Platinum mileage differential. Also, I had previously been told that Delta was giving NW
elites 50% mileage credit on K, L, and T coded fares, but I've been assured that's part of the negative rumor mill surrounding this alliance.
It was just a matter of being sure everyone was doing the same business the same way. That way everyone