As a follow on to my previous post yesterday, I have been looking for AA codeshares in Asia. I can find some e.g. AA 8486 from BKK to HND operated by JAL. Can these codeshares be used if they are not immediately followed/preceded by a trans-pacific flight. I'm not sure if they are available independantly or if the agreement between AA and JAL is to allow more destinations to/from US and hence carry additional constraints on usage.
So far I've found AA codeshares with JAL/Cathay for BKK, SIN, CGK, ICN, SGN and DPS but nothing in Australia or NZ
I'm not a ticket expert but what seemed to work for me was checking if the route was bookable on the desired codeshare airline's website. So for example if you want to fly from A to B with an AA flight number then see if you can book the desired flight on the AA website with AA codeshare flight numbers. If not you most likely can't book it because if the marketing airline doesn't let you book it then who will?