What about calling the airline direct (undoubtedly needing to do it frequently)? On hight density routes, like JFK-LAX or JFK--SFO, I call and ask if anything in the inventory is available for upgrade. On DL's route (they have 7 non stops a day JFK-SFO) I can usually find one of the flights available for upgrade at the time of ticketing. Not so much AA. Ironic, since DL's FF program is generally the stingiest.