United Airlines has pledged to add flights at Chicago's O'Hare International Airport to prevent American Airlines from gaining gates at its expense, reported Reuters.

CEO Scott Kirby told analysts the carrier would add "as many flights as required" to maintain its gate count. He said United earned about US$500 million in Chicago in 2025 while American lost a similar amount, and warned American's losses could widen to $1 billion in 2026.

Mr Kirby said United now holds a 22 percentage-point lead among Chicago customers and a 38 percentage-point lead among business travellers, reversing what he described as American's advantage a decade ago. American did not immediately comment.

The dispute centres on gate access and schedules, critical for attracting corporate travellers. United operates about half of all flights at O'Hare compared with a third for American.

The gap widened in late 2025 after a city reallocation gave United five more gates and cut American's total by four, a move American unsuccessfully challenged in court. American has since agreed to buy two gates from Spirit Airlines for $30 million and is expected to be awarded three more later this year.

United plans nearly 650 daily departures this summer to about 200 destinations. American has announced its largest spring schedule at O'Hare, adding around 100 peak-day flights to lift its total above 500 daily departures.

Chicago remains one of the few major US hubs where two legacy carriers operate at full scale, unlike Atlanta, Houston and Dallas, where one airline dominates.