I want to do a RTW in economy (L class) and because of the mileage earned I need to travel on AA, AY or LA (codeshares included).

I want to go Europe->North Am->Asia->Europe
I can use AA to get LHR->N.A.
Then AA for 6 hops in N.A.
Then AA to go to NRT or HKG
??? for 3/4 hops in Asia
Than AY to go to HEL
??? for 3/4 hops in Europe finishing in LHR

My question is, can I find somehow the codeshare routes of AA,AY,LA which are in Asia (not intercontinentals) and which are in Europe.
All AY flights in Europe which I saw were from HEL, which is quite understandable. I was looking on routing: HEL-LIS-HEL-MAD-LHR with last segment on LA codeshare. This codeshare can be found in the 'where we fly' oneworld map, but I cannot find any availability on this route.

So can anyone give me any pointers to codeshares?

As regards AA codeshares in Asia, you can only book the codeshare in connection with a flight to/from the U.S. This means that you could fly, say, JFK-HKG-SIN all on AA codeshares operated by CX. After this, you won't be able to avoid CX or JL as marketing carrier. Anyway you should get 70% of miles on JL IIRC. So fly AA codeshare to NRT or HKG and a further destination beyond the gateway and then use JL in Asia.

The same could work for your last inter-Asia segment connecting to your AY flight to HEL. However I am not aware of whether AY has any codeshares to/from HKG or NRT. If you find some, you may route xxx-HKG/NRT-HEL all with AY as marketing carrier.

The ideal route would therefore be sthg like ...xxx AA HKG AA xxx JL NRT JL xxx AY NRT AY HEL...

In Europe AFAIK LA codeshares are bookable only in connection with a flight to/from Chile. Therefore you cannot book MAD-LHR on LA as a standalone segment. You have to book with IB.

Edited to add: I played around with the oneworld interactive map and I could find one single AY codeshare on the HKG-BKK route. Unfortunately, the same does not exist in the opposite direction. So this would be an option for an eastward RTW (HEL AY HKG AY BKK), but not for an westward one. Flight in question is CX713/AY5843.

How about Mal�v?

They also award 100% AA miles on L class fares, although no elite status bonus.

The problem is that I want the platinum 100% bonus. And this is valid for AA, LA and AY only. Therefore AA,LA,AY earns 200%, while all others earn 100% or less.
Japan earns 70% which is almost a third of AA flight.

Now you can see how important is a codeshare

JFK-HKG-xxx all on AA codeshares look like a must
xxx can be NRT for convenience or CGK/DPS for ~500 extra miles

Now I was reading AA timetable and I found some interesting codeshares in Europe
You can fly London-Amman on RJ coded under AA number for 2291*2 miles without requiring US connection. Very nice Also Paris-Amman, for nice routing Paris-Amman-London, all for 200% mileage to AA