Chicago's O'Hare Airport is the world's 8th-busiest with over 80 million passengers in 2024. Chicago is the focal point of an old rivalry: American Airlines (hub) and United Airlines (home base). Chicago is different Chicago O'Hare is one of the few airports in the United States where two major airlines operate competing hubs. This is not just a marketing stunt, but rather a real, visible fight over gates, schedules, and the corporate travelers who really pay the bills for these carriers. Like every major airport, O'Hare is constrained. Disruptions at O'Hare have serious consequences. While the city's general budget is in a deficit, O'Hare is operated as an Enterprise Fund. This means its finances are separate from the city’s day-to-day "Corporate Fund." Expansion is funded almost entirely by airline fees, federal grants, and airport revenue bonds, rather than your property taxes. The city is facing what many experts call a "financial reckoning." Chicago owes roughly $36 billion in unfunded pension liabilities. In late 2025, S&P Global Ratings shifted Chicago's outlook to "Negative." The city recently broke ground on Concourse D ($1.3 billion), which is the first major milestone of the larger Terminal Area Plan. O'Hare is adding 19 new single-aisle gates, with the flexibility to convert them for larger wide-body aircraft. Vertical construction is slated to begin in Spring 2026, with a targeted completion date in late 2028. Two planned "Satellite" concourses will act as a pressure valve for the airport while more intense construction happens elsewhere. The centerpiece of the expansion is the O’Hare Global Terminal, which will replace the aging Terminal 2. For American vs. United, there is an ongoing scramble for runway slots, taxi space, and gates. United and American, which pay the bulk of the bills through fees, have expressed concerns about the "ballooning" $8.5 billion+ price tag. To add to the pressure, O'Hare is busier than ever, with flights up ~10% over previous years. Although Chicago is home to United, American has served the city since 1926. In 2002, the competitive balance shifted dramatically when the city of Chicago removed all slot restrictions at O'Hare Airport, allowing American Airlines to immediately expand its regional flights there to further compete with United Airlines. American acquired TWA, then was acquired by US Airways, and the focus switched to Charlotte, DFW, and Phoenix. The numbers tell a dramatic story. United trailed American at O'Hare in 2019, 30% to 29%. At the end of last year, United led 51% to 29%. The Gate Fight The Chicago Department of Aviation assigns gates based on the number of flights each airline made into the airport during the previous year. AirlineGeeks This creates a "rich get richer" dynamic: the airline that operates more flights gets more gates, allowing it to operate even more flights. American filed a lawsuit against the city of Chicago, claiming the gate reallocation violates its 2018 lease agreement and is part of an effort to "marginalize" American. The airline argues that eroding the dual-hub structure would harm Chicago's competitiveness. United CEO Scott Kirby made headlines in January 2026 by declaring, "We're not going to allow them to win a single gate at our expense in 2026. We're going to add as many flights as are required to make sure that we keep our gate count the same in Chicago." He added: "The color will be [we] will be in the black while American is in the red." The rumble between these two airlines goes a long time. Old hands will remember the days of Steve Wolf (United ) vs. Robert Crandell (American), especially during the international route cases. Great times! The Data Picture As is our modus, we like to turn to the data to see what itcan tell us. Using the US DOT On-Time dataset, we compiled these charts. O'Hare as the origin point The chart has four parts, numbered 1-4 Even before the pandemic, United was the dominant airline Coming out of the pandemic, chart 3 shows United doing far better in operational terms, confirmed by chart 4 It's clear, though, that O'Hare operations are experiencing rising delays [caption id="attachment_186760" align="aligncenter" width="580"] US DOT; AirInsight[/caption] O'Hare as the destination point The chartalso has four parts, numbered 1-4 Notice United's rapid recovery from the pandemic in chart 1 American trails operationally in Chart 3, but is doing better with taxi-in (Chart 2) Chart 4 confirms what we see with O'Hare origin traffic - the airport is seeing rising delays [caption id="attachment_186761" align="aligncenter" width="580"] US DOT; AirInsight[/caption] Bottom Line O'Hare is a crucial location for two of the US's largest airlines. Airport delays are a growing concern. Especially when you consider that American's operations cost/minute is ~$118, and United's is ~$92. Every minute delayed is lost with no chance to recover, as costs keep going while revenue is fixed once a ticket is sold. American is at a cost disadvantage, probably making it even more determined not to lose its place at O'Hare.