Aaaand the AAdvantage F space on JAl for tomorrow is gone. Probably just meltwater from the AA glacier descending on their single overworked Raspberry Pi. My advice is just use the tools and counter-check against BA.com. There's very unlikely to be any mistakes like this, so long as one searches only for direct flights, longer-term.

I am going to write to seats.aero to see if they'll add several JAL routes for long-term monitoring using the Alaskan API, which shows the same availability as BA. That's the ideal solution. In any case, good luck again with your flight!