Check in at AA or JAL for First?
 

Forgive me I have lost my Frequent flyer skills due to Pandemic. If I am flying First HND to LAX on a AAward ticket that has both a AA flt number and JAL flt number can I check in at JAL counter if I wanted? Does it make a difference in Japan? I imagine going from LAX to HND is does not matter much.

If it's JAL's metal, then check in with JAL.

Check in with whichever carrier is operating the first leg.

Hmm, AAdvantage award tickets are only ever booked with the operating carrier's prime flight number, no codeshares. So not really even sure why this reservation would have both, unless OP means it's an AA flight number in one direction and an JL flight number in the other direction.

I was wondering this too; the whole thing doesn't make any sense. But it doesn't matter, you just check in with the first operating carrier and ignore everything else

OP probably means he has both an AA PNR and a JL PNR.