AA and UA can't compete effectively with MT and VS. They don't have the right product or fare structure. AA also suffer with Oneworld passengers being actively routed via DUB and bypassing their joint venture with BA. DL slightly ahead of the other US carriers with its ownership (partial) of VS. What can UA do? Their Codeshare with SQ might help a little going forward. Otherwise their options appear to be to withdraw or engage in a price war. DL have hinted at this elsewhere in regards to Norwegian. I suspect New York may remain strong enough for UA and AA depending how heavily MT, DL/VS and DY choose to go on the attack. At one point MT filed for double daily JFK, but then retracted. AA might be able to go the way of DL and get BA to operate, but not really sure of any merit there. Most likely is that these two giants will choose to deploy their assets elsewhere. I think MAN suits the smaller competitor airline over the behemoths. As soon as UA took over CO there was decline. Similarly, AA with US.