The U.S. Department of Transportation (DOT) has launched an investigation into the frequent-flyer programs of the four largest U.S. airlines—American Airlines, Delta Air Lines, Southwest Airlines, and United Airlines—following numerous consumer complaints. The inquiry, spearheaded by Transportation Secretary Pete Buttigieg, focuses on potential unfair, deceptive, or anticompetitive practices such as the devaluation of earned rewards, hidden or dynamic pricing, additional fees, and reduced competition and choice. Airlines have been asked to provide detailed information on these aspects, including how their policies have changed over recent years. Buttigieg emphasized the importance of transparency and fairness in these programs, as many Americans rely on them for significant travel expenses. The investigation is part of a broader effort by the DOT to ensure consumers receive the promised value from loyalty programs.