Hi all - I wanted to post another data point, having booked an itinerary all on JL metal through AA, JFK-NRT-TPE, TPE-NRT-JFK, the long haul flights having AA flight numbers and fare classes, D, D, X, and I. After getting my JL PNR from AA, I was finally able to retrieve my reservation on the JAL US site using the combo suggested above of AA flight number, JL record locator, last name, and first name (NO middle name needed). I was then able to select seats, which are NOT shown in my reservation on AA's website, but still showing when I retrieve the reservation again on the JAL website. (When I called AA for seat selection, the system robot confirmed that the seats had been selected, however.)