Originally Posted by bzcat

CX being a founding member of OW has veto power for any new member so CZ is likely not going to be a OW member anytime soon. If CZ had the agreements to join OW, it would have been announced at the same time as pulling out of ST.

The only airline name mentioned in the press release was AA so it seems clear that CZ pulling out of ST is probably influenced by AA, which has a minority stake in CZ.

AA is probably doing a lot of behind the scene maneuvering to ensure ST airlines, and DL in particular, don't get a huge advantage at the new airport in Beijing. With CZ and MU both moving to the new airport, ST was going to dominate the operations there. But if CZ is out now, it ensures that there will be at least one non-ST network hub airline at the new airport so the balance of power doesn't tip too much in favor of ST carriers. That's probably the main objective. Having CZ in OW is an added bonus but not really the main objective.