I have an AA code share on JL in Aug23, ORD to HND. I have the JL Record Locator and tried
NUMEROUS times via their (JAL) website and calling into AA reservations, to select my seats. It CANNOT be done!!! Even tried calling JL USA number but they will not take your call if the flight doesn't leave with 48 or so hours!
Perhaps it is only because the flight is still months away, but AA told me, sorry, select your seats at the airport! This is the message I have received EVERY TIME on the JAL INTERNATIONAL seat selection page...no matter how I enter the flight number, names, and the record locator. So don't count on pre selecting seats on JL when booking via AA code share!