Not to sound too legalistic, but they have no case whatsoever. There is no injury to any party yet, so the case is not ripe. You can't sue someone for what might happen in the future.
They also don't have any standing in the case. Only a party that has some kind of legal tie with the two companies may seek an injunction to stop the merger. Since neither company is required to fly any passenger in the future there is no tie. It will be thrown out with the quickness.
New K Now