I'm a bit new at this, so thought I'd ask....
I have a One World American Airlines frequent flyer number.
I also have a Cathay Pacific frequent flyer number.

When flying Ord - HKG, which number should I give them?
Doesn't giving them my AA number get me mileage credit on Cathay, as well as all other One World partners, but giving them my Cathay number only gives me credit with Cathay?

1. You can only earn mileage for one airlines.

2. You can earn mileage or not depends on your booking class and how the ticket is issued.

Provide more detail if you can.

if you have a status in one airline, say sapphire with AA but wish to build up MPC status you can do this:

Give the AA OW Sapphire membership. This entitles you to all the benefits associated and may even put you ahead of que for op-ups

AFTER the pax manifest printed and flight closed for sure, you demand your AA FFP to be removed and CX FFP number printed instead. This way you are still "recognized" as One world sapphire onboard (for what its worth... greeting? perhaps) but u get miles/poitns to CX to build up.

To be really cheeky, if your MPC membership is about to expire, you can choose NOT to have your miles creditied by removing the FFP# all together... then after your membership rolls u request missing miles into CX after new cycle starts.

All very grey-area but maximize the benefits.

I tried that a few years ago, but it was not successful. Acocrding to the airport agent one can only change FFP but not remove it once added. Was your experience different?

If you are on coach, only booking class H and above qualifies for AA points.

I think they are lying just to reduce workload. You can make up excuses like "I'm going to join AA FFP but I have no membership# yet so I need to have this removed" should be ok.... it's all about how you phrase it, I think.

No, the first time they (YVR agents) tried hard and even put 0000000 (which showed up on my BP) instead of my membership number. The miles was still credited to my account in 2 days. The second time the agent told me FFP can only be changed but not removed, which would make sense after my previous experience.

If you use MPL GO/SL to book a CX ticket then change the FFP to AA null at the check in, are you still geting these loundge invitations and luggage allowances that CX offers to its GO/SL?

I guess you can still show your GO/SL MPC card in order to get into the lounge?

you should technically change your elite status at last minute after op-ups have been processed, and the manifest (for the flight crew) printed.

If you change them at check-in, you sometimes loose your perks. For example heard of a guy who was op-upped at check-in, asked to change from GO to AA card and was told they will have to rescind the upgrade if GO number wasn't present.

Card should get you entry to lounge.

Interesting, how? Give your other FFP membership card to the ground agent as soon as she/he prints out the manifest?

precisely so.

or can do in lounge, cuz gate agent will be busy as nutz. i'm sure they get these sorts of request frequently. I've done it. but I must admit "removing FFP #" is only a word of mouth (i.e. anacdotal evidences) and I don't have first-hand account, as I plan my requalifying travels

I might do a DONE6 next year - with all these long haul J/A flights, I will requalify as a CX GO (60,500miles) if I credit all miles into my MPC account... however if I give up renewing my MPC status and use my QFF Bronze as the FFP, I will qualify as a QFF Platimun (1450 credit status) when I finish...

Although QF WP might not be as good as CX DM, I'm not sure about CX GO though...

It used to be easy .. but AMADEUS has a very bad thing in that it 'remembers' the first FFP that was put on it.. and with the old system, the agent will just add the FFP you want on the flight that you're taking. It won't work with the new AMADEUS system. The gate agent must physically remove the old FFP entirely otherwise the system will remember the first FFP and credit that one even though your BP may reflect the new number.

The check-in system will still be in CUPAC, at least until sometime in 2013, before moving to Amadeus Alt�a.