Originally Posted by
JALPak
Actually no, go talk to AA and only AA. This is marketed by AA and seat assignment should be taken care of by AA. Also note that unassigned seats aren’t necessarily available to codeshare passengers so AA’s hands can be tied too given the drastic reduction of the PY cabin.
https://faq-en.jal.co.jp/app/answers/detail/a_id/26696
This is what I hate about these code share agreements. AA will send you to JAL for the seats. When you complete the booking via AA it will tell you that you have to contact JAL for seats.