Earning miles on *A codeshare flight operated by another *A partner (Neither UA)
 

I'm pretty sure I know the answer to this but want to check with those more knowledgeable.

On an AC 014 stock but a LH operated AC code share segment (AC flight number) the UA earning would fall under the LH chart based on fare class not the AC chart correct?

Correct; simple *A rule, the flight operator determines the earnings, not the flight marketer.

Of course WineCountryUA is correct. However, good luck figuring out what the fare code is between AC and LH (or any *A partner) before you book the flight. You will see the AC code you're booking but that won't translate to what LH sees it as. And LH is what will matter for credit to the UA MP program. You may be booking a 50% code on AC which translates to 25%, etc. This is the biggest single downfall of codeshare booking in *A (IMO).

-RM

Thanks, I had not considered that factor. UGH. And I suppose good luck getting using plus points even if it ends up being an eligible LH fare class.

LH only allows the application of PlusPoints on native marketed LH flights (no codeshares)

Correct. But typically with UA codeshares isn't it possible to call the mileageplus line to have that segment switched?

Yes but such a change is not likely to happen on 014 ticket stock / AC codeshare

Right; only AC could do it.

The fare mapping problem might not be as bad as it sounds: AC, UA, and LH group have harmonized their economy fare classes for TATL routes, so I suspect the mapping would be one-to-one. But the lack of a native flight number would be a killer -- and I don't know if AC agents could be persuaded to make that change and reissue the ticket in order to allow you to apply a UA instrument, especially if there's no inventory available under the native flight number.

The fare codes are only somewhat harmonized based on cabin but not based on earnings. For example:

AC P earns 200% while LH P earns 100%.
AC Z earns 200% while LH Z earns 150%.
AC O earns 150% in PE while LH O is ineligible.

Many other differences as well. So to my point to the OP, be careful what you book and do not assume what you book on AC is true for LH. However, I believe the paid earning fare classes of AC will net you miles through LH (just possibly not at the same rate). You can always call LH after you book the itinerary and see what fare code you were assigned. I don't know the rules of cancelling an AC ticket within 24 hours for a full refund if you're not happy with the LH class. Or maybe it's just easier to book through LH in the first place.

-RM

Premium Economy is the least "harmonized" fare class
AC uses O, E, N
LH uses G, E, N
UA uses O, A, R

AC O would likely map to LH G which is 150%

How about when the marketing carrier is not a *A member or is a connecting partner?

All that matters is the flight operator and your MP account is entered on the PNR.

translating booking classes can, however, become a real nightmare

Can each segment be associated with a different FFN?

I have a UA marketed NH operated flight in P, first thought was crediting to VS for 150% but I'm not sure that would work since they're not star alliance, if not then probably crediting to AC at 100% since the ticket stock is UA.

Also there a random 7G flight with NH number that only earns on NH, I'm assuming I can just ask the gate or checkin agent to switch FFN for one particular flight only?

UA issued tickets can only have a single crediting program. You can try to change programs between flights but since most carriers do not post immediately you can end up crediting to wrong programs. If there is sufficent time between flights and the first flight has posted then it is safe to change the second flight.