Sorry if this has been asked already but seeing if you can help so I know my options. I am currently booked on a one way flight JFK>HND>BKK using AA miles all on flights operated by JAL, in premium economy for both segments (I booked this a long time ago and business wasn't available). Say for example, closer in, I search AA and business class opens up on the JFK>HND portion, but the HND>BKK portion doesn't have any award seats left (neither business, premium economy, or economy). Would it be possible for an AA agent to upgrade the JFK>HND portion and keep my HND>BKK portion in premium economy as is, or would that not be possible?

Thank you so much!