AAdvantage Elite on Aer Lingus codeshare
 

Flying BER-DUB-DFW. The first flight is an AA flight number on a Aer Lingus flight
For the EI flight, will I get AA checked bag benefit for AA PLT? What about carryon bags? Seat selection? Lounge in Berlin?

I haven't personally flown one of these, but I did enquire with an AAgent about an EI flight to begin a trip:
No checked bag, although I'd argue that the "most significant carrier" rule would apply here, which would allow you one.
I don't think EI has fares that don't allow carry ons, but in this case the EI rules would apply.
No free seat selection (every seat is a paid seat).
No lounge, although some Eurobiz fares do come with lounge access.

There are no AA elite benefits on EI.

The AA bag fee schedule (but not elite bag waivers) will apply to your itinerary because AA is both the first marketing carrier and most significant carrier: you will get 0 free bags if you booked basic economy, 1 for standard economy, 2 for premium economy or business, and 3 for first.

You will be able to take a 10 kg carry-on bag aboard because you are connecting to an interline partner (see this aerlingus.com page on carry-on bags).

All economy seat selection on EI is paid unless you are an EI elite.

No lounge access in BER unless you have EI status (since you are on an AA* codeshare it's not possible for you to have purchased an Advantage or AerSpace fare which would get you lounge access).

VFR I wish I had seen your answer before I posted a similar question in another forum. To add on my own flare to mvoight's question:

My flight will be similar: DUB-LHR-PHL with DUB-LHR on EI w/ AA codeshare and connecting to LHR-PHL on AA. I am a BAEC Silver/Oneworld Sapphire. The ticket is an AA coded Main economy cabin ticket. If I'm understanding you correctly, because my DUB-LHR leg is on EI metal, I will not get fast-track at DUB, I will not be able to pick a free seat on EI, I will not have priority check-in at DUB, and I will only be allowed 1 check-in bag even though in theory I am allowed all of these things if I were flying AA or BA metal. Is this correct? (I really hope I'm wrong on this one)

OW benefits apply only when on flights both marketed by and operated by an OW airline
Since EI is not an OW airline, no OW benefits apply

TL;DR: Flying economy without status sucks. This is pretty much universally true.

Thank you. Don't like it but at least now I know. And I guess I shouldn't hold my breath that EI will rejoin OW anytime soon, eh?

Maybe, but probably not before your flight

Forgive my ignorance, but why did they leave in the first place? I remember they were a founding OW member. It would be great to have another European carrier in the mix.

Their "strategy" of being a low cost point to point carrier didn't fit in with the rest of the OW carriers, aka leveraging their hubs for higher cost complicated routings.

I have an upcoming itinerary that was book via AA.com in main cabin (NOT Basic Economy) ORK-LHR-DFW.
am OWE via my EXP.

ORK-LHR is EI-operated but is a codeshare with an AA flight #. I have purchased seat 2C, for whatever that's worth...
LHR-DFW is AA-operated, with a SWU applied and confirmed at booking.

What is my baggage allowance when I depart ORK? I will need to check one bag (golf clubs :)).

Normally i can wrap my head around these codeshare issues, but don't want any surprises.
Thanks!

I think it's up to EI, but check your receipt from AA (it should have been emailed). They have to give you at least that much.

My receipt from AA shows one free checked bag, although I know that my EXP benefits trump that when i check in with AA on my outbound.
If EI decides to charge me for my first bag, is this something that anyone has had luck having AA refund after the fact?

I find it odd that the bag allowance for the entire itinerary is not equal to my allowance with the marketing carrier (3 bags as EXP...).

If your booking shows an allowance of 1 piece , there is no reason to think that EI will chatge for the 1st bag. There is nothing odd that benefits associated with status on AA do not carry over to other carriers

This whole EI codeshare is ridiculous in its implementation. It's an airline "friends with benefits" without EI rejoining the alliance. EI is like the GOL tie-up in that it's really a low cost that happens to fly business on widebodies across the water but everything from seat assignments to luggage allowance isn't well handled from a systems perspective. It's great to want to sell seats on everyone else's metal but at least take the time to do it right.