As the U.S. Department of Justice investigates whether airlines conspired to keep ticket prices high, consumers are already going to court.

Quinn Emanuel Urquhart & Sullivan on July 6 filed an antitrust class action against American Airlines Group Inc., Delta Air Lines Inc., Southwest Airlines Co. and United Airlines Inc. in the U.S. District Court for the District of Columbia. Quinn Emanuel partner Stephen Neuwirth, who chairs the firm’s antitrust practice, is lead counsel for the plaintiffs.