Originally Posted by ernestnywang

What I meant to say was you could remove the FF number altogether, and then have the reservation staff add it back only to selected segments. The SSR (Special Service
Request) of FF number looks like this and there are two different ways to enter them. CX accepts both (note most airlines accept both, but not all).
SSR FQTV CX HK/ CXxxxxxxxxxx SAPPHIRE/GO
SSR FQTV CX HK/ CXxxxxxxxxxx SAPPHIRE/GO/S3
In the first form, the membership number is entered to all CX segments. In the second form, the membership number is only entered to segment number 3. Note that names take up lines as well, so for a one-person PNR, the first segment would be S2.