Is CX a UA partner?
 

I am able to book RDU-SFO-HKG-HGH on united.com in J. The last leg is on CX. Wondering if will earn UA miles on the last leg or should I give Cathay my AA number so that I can earn AA miles (not interested in CX miles). Thank you.

In Star Alliance ff earnings are based on the operating carrier when an eligible marketing carrier (flight number)
In Oneworld Alliance ff earnings are based on the marketing carrier (flight number) when an eligible marketing carrier.
For those revenue based ffp's can be more complicated.

UA is just being a travel agent in selling the last flight. UA & CX are not partners.
Best to credit the CX fight to AA or another OW airline ffp

Thank you so much. Will do.

spot on and for UA in Star Alliance you are going to need something like Air China/Shenzhen Airlines or ANA HGH flights. The CX flight needs AA/AS Oneworld Alliance FFQs

Associated question.
Flight is LH stock and flight number on CX metal.
Can.this earn.to United?
Or if.not QF as a.one world member.
Many thanks for your advice.
WLGNZ

You can only put that flight on LH M&M or CX. I don't believe any other programme would credit it for you.