Originally Posted by ernestnywang

No. A TA may be able to view the PNR in certain cases, but certainly will not be able to claim a ticketed and partially flown PNR/ticket from airline.
Other oneworld carriers theoretically can take over the ticket and re-issue it on their own stock (with the possibility of recalculating YQ/YRs). I think very few are willing to do it these days and will likely ask you to go back to AA. Another layer of complexity is that AA and AS use Sabre, while all other oneworld carriers use Amadeus. While chances are still low, you might have a slightly better chance to ask the carrier of your next departing flight to take over.