Originally Posted by pgh234

Yes...those are married segments that you published. For example, if you just searched AMS-JFK, you will find Z = 0 on your flight, that would just be a single segment. DL upgrades by segment for the moment on DL operated flights and OP space must be available on a singular flight.

For KL operated flights...no one really knows what the "real" rules are. I had the same situation as you when I upgraded. Z was available on the married segments and not available on the single segment.