United Airlines operated a MileagePlus frequent flyer program that allowed customers to collect rewards such as free flights and seat upgrades in exchange for patronizing United. MileagePlus rules allowed United to change the terms of the program unilaterally and without notice. United offered a Million-Mile Flyer status to Mileage Plus members after they had flown more than 1 million miles on United. Reaching this status offered additional benefits. After seeing the advertisements for the million-mile program, George Lagen changed from using other airlines to almost exclusively patronizing United. In 10 years, Lagen became a million-mile flyer and received the upgraded benefits that came with this status.

However, after United merged with Continental Airlines, the airline substantially reduced the benefits of patrons who were million-mile members. Lagen sued United, alleging that United breached a unilateral contract. Lagen argued that United made an offer for a unilateral contract, and his performance of flying over 1 million miles on United created a binding unilateral contract. United argued that no unilateral contract was formed because it reserved the right to change the terms of the program whenever it wanted. Lagen appealed. Was a unilateral contract formed when Lagen flew 1 million miles on United? Lagen v. United Continental Holdings, Inc., 774 F.3d 1124, 2014 U.S. App. Lexis 24216 (United States Court of Appeals for the Seventh Circuit, 2014)