I am building status in the Marco Polo Club, so my flight is associated with that membership. However, can I still use my Emerald status via AA to get into the First Class lounge, even though it's not on my ticket?

Yes. Two ways.

1. Just show proof of your emerald status where needed, manually.
2. Get a reservation or check- in agent to put your AA Emerald status in the FQTS (status) field on your booking, leaving your MPC number in the FQTV (value) field. This will then reflect your status on your boarding pass and to crew etc. But check that they don't mess this change up as the usual thing would be to have the same number in both fields, and some agents don't understand.

Awesome! Thank you for the response.

just be careful inputting the AA number. I can't remember the thread or discussion exactly, but CX was trying to crack down on people getting benefits from two different OW membership programs a while ago. I don't remember all the details, nor if it was very effective.

Thanks... Wished I had asked the questions as the OP had a few days ago. In the same situation as OP. Last time I was on CX as OWE, I seemed to fair well with op-up situations. Just didn't think the same would occur going solo with my MP account.

These days, opups are harder to come by for OWE. I've seen so many MPC Green members op-upped before me (a OWE). I don't think my spend on CX is that low either.

Call it maybe first-timer's luck as last summer was my first time ever flying CX. My route (SFO-HKG-ICN-HKG-SFO) in PE. Maybe the system flagged me as such and the rest is history.

Was op-up'd (SFO-HKG and ICN-HKG). Head purser greeting me as OWE on each leg and offered me a bottle of water when in PE. Now, I'm still on the fence if I want to switch over the MPC while I am OWE status. Most of my new flights will be in the Americas and I'd miss those AA domestic upgrades and and SWU's for whatever their worth at times.

In a few weeks I'm only using CX for HKG-ICN-HKG in PE) but have AA for my legs to/from HKG out of SFO. Figuring it would be better to be OWE in PE over no-status MP in PE. Last summer my PE aircraft from ICN-HKG was swapped to one without it and my ticket was re-ticketed from E to L fare but they i was placed into J. Hmmmmm... Still kinda sore about it as L fare gets me no crediting on AA.

i've not done this on CX personally but what I have seen on other carriers is only the FQTV field is printed on the bus pass. Kinda makes sense as if there is a retro credit issue the FQTV field is needed, anyone in the airline who needs to check your status can do it online these days.