Originally Posted by
ricktoronto
I failed to think that 1/2 of a R/T was counted as such, so it is slightly less awkward (e.g. losing less value per trip) than I thought looking at cxfan1960's analysis above. Still a weird system losing 90 perfectly useful points to get SL then losing 50 more to get to GO and so on.
You are likely to lose CP when upgrading a tier, but the most CP you can theoretically lose should be 130 CP. Because the most you can earn on a sector is 135 CP (F class HKG-JFK etc.); in this unfortunate scenario you would've been 5 CP away from SL, GO or DM prior to the cash fare ultra long-haul F class flight. Obviously this is extreme, few people actually lose 130 CP. Roughly speaking, losing >50 CP is bad luck. 20-50 CP might be fairly typical. Losing <=20 CP is a "win". Fwiw, there are reports on here of CX being flexible for people just missing a higher tier, or tier renewal based on CP crediting issues.
The closer your "Distance from Higher Tier" (DHT) is to equaling CP earned from the "Flight Over Threshold" (FOT), the less CP lost upon upgrade. Of course if you're lucky enough where DHT = FOT, you lose nothing.
Note this is only applicable for people going up the tier hierarchy. If you're any of SL, GO or DM already and will stay in the same tier going forward, there is no loss. And GOs and DMs now have Mid-Tier benefits which make it a little more lucrative to keep earning to MPC despite requalifying.
One other thing to consider is the way CP timing works. CP is credited to your account on the actual
posting date, not retro-credited to the flight timing date. So there is both latency and arbitrariness to the timing; this is especially true for partner OW flights, which tend to credit slower, less-predictably, and don't hit at all sometimes.