A federal judge has rejected an attempt by American Airlines (AA, Dallas/Fort Worth) to delay the transfer of four gates at Chicago O'Hare to United Airlines (UA, Chicago O'Hare), according to local media reports.

American had filed a preliminary injunction to stop the gate reallocation, which was scheduled for October 1, but a Cook County judge denied the request.

In a statement to ch-aviation, American Airlines said: “While we are disappointed with the court’s ruling on American’s request for a preliminary injunction, the court clearly found that the city made an agreement with American in 2018.”

American Airlines is pursuing a breach of contract lawsuit over a 15-year deal reached with United and the city in 2018. This deal included a clause that oversaw future gate assignments, which was allegedly violated in early 2025 when United requested a reassessment of terminal positions, a move that will result in American surrendering four positions and United gaining five, according to the carrier.

“We believe that agreement would have ensured that future gate assignments start from a fair playing field to maintain the balance of the nation’s largest dual hub. That was not honoured during the gate redetermination process,” American added.

The carrier argued that any reassessment would have had to have taken place after April 2027, not sooner. “The premature trigger of the gate reallocation will give one airline a competitive advantage from the start. But we remain committed to Chicago and to preserving competition at O’Hare,” American said.

Meanwhile, in a letter to employees, United's president Brett Hart said the judge's block of American's injunction was more than a legal victory, it was a "powerful validation of United's growth, investment, and incredible workforce" in Chicago. The company is helping to drive record-breaking passenger volumes at O'Hare, and with the five new gates "We're ready to seize this opportunity and grow even more," he added.

According to ch-aviation schedules data, United Airlines holds 48.16% of the overall capacity at the airport, followed by American Airlines with 32.78%. All other carriers have less than 5% with Delta Air Lines holding the largest remaining share with 3.47%.