Originally Posted by number_6

No, what I wrote was for HEL-HKG(AY)-AKL(CX) it was the AY allowance. I misread your post and thought for some reason you were flying AY only for WAW-HEL and not HEL-HKG. So, AY is the MSC for this trip and the AY allowance applies to the entire trip. Sorry for the confusion, I know CX doesn't fly to HEL (and back).

The MSC rule is the airline flying between IATA areas (Europe/Middle East/Africa is one area, and Asia/Pacific is another area), if not flying between areas then it is airline flying between subareas, and if the whole trip is within a single subarea, then the airline flying the first international sector. For this trip HEL-HKG is the sector that determines which airline is most significant carrier.