My guess is LAS or Phx. The need a way to get around the California rest and meal break laws. American announced the pull-down of their sfo crew base as a result of the courts ruling that flight crews are not exempt. All flights 4 hours require 10 min off duty. And 5 hours require 30 minutes. A city with hourly flights close enough to still do transcontinental service in a single duty is what they are after, my guess. I have noticed that on the fa side there are extra crew when there are California based crew working longer flights