No, I don’t think this is a code share, I’d called it a joint ticket. The AS flight doesn’t have an AA flight number, and you can’t buy this itinerary from AS, only from AA. Alaska sells the opposite of this on some flights through Chicago that connect to Anchorage using AS. You fly the short leg to ORD on AA, with an AA flight number, then AS the rest of the way to either Anchorage or an outlying community in Alaska and you can’t buy that ticket from AA, only from AS. Have to see if the Emerald One World rules apply for checking in with AA because it would be a ticket purchased from Alaska. Based upon starting these short flights to ANC in both OME and BRW in the past year, the AS baggage rules apply, but my experience has been that you can’t get upgraded at the airport or before by AS, even to premium class when the fare basis allows a free upgrade upon purchase, based upon AS elite status. Exit row seating was possible though.