Last week, American Airlines, Delta, Southwest and United Continental received some unwelcome news. A federal judge denied the airlines’ motion to dismiss a class action alleging a price-fixing conspiracy. The plaintiffs allege that the airlines colluded to raise fares and reduce flight choices for travelers, in part by restricting seating capacity in their aircrafts. (The case is In re Domestic Airline Travel Antitrust Litigation, U.S. District Court, District of Columbia, No. 15-mc-01404.) In addition to the class action, The Department of Justice is conducting its own separate inquiry into the matter.