United & American's Chicago O'Hare Turf War Continues: Who Will Win?

Chicago O’Hare International Airport (ORD) is rare in that it is a hub for two of the largest airlines in the US: United Airlines and American Airlines. Only a handful of other airports in the US play host to the two carriers, with Los Angeles International Airport (LAX) being a prime example. This has led to stiff competition at the airport, with the two airlines battling it out to win passengers on some of the country’s most prestigious and profitable routes.

In this article, we will take a look at the competition between United Airlines and American Airlines at Chicago O’Hare International Airport, using data from Cirium, an aviation analytics company, to examine the routes operated by each carrier.

United Airlines At Chicago O’Hare International Airport

Photo: Colin Cooke Photo | Wikimedia Commons

The latest data from Cirium shows that in August 2025, United Airlines plans to operate a total of 35,235 flights to and from Chicago O’Hare International Airport, offering more than 4.2 million seats. The Star Alliance carrier commands a 40% market share at the airport, with its busiest routes by number of flights shown in the table below.

Unsurprisingly, the majority of United Airlines’ busiest routes from Chicago O’Hare International Airport are to the carrier’s other major hubs throughout the US, such as Newark Liberty International Airport, Denver International Airport, and San Francisco International Airport.

United Airlines also offers an average of more than ten flights per day on busy commuter routes throughout the region, including to New York LaGuardia Airport and Ronald Reagan Washington National Airport. How does this busy operation compare to that of American Airlines?

American Airlines At Chicago O’Hare International Airport

Photo: Vincenzo Pace | Simple Flying

By contrast, American Airlines has a total of 27,558 flights scheduled to operate to and from Chicago O’Hare International Airport in August 2025, offering more than 3.1 million seats. This makes the oneworld carrier’s operation at the airport around 25% smaller than that of United Airlines when measured by the number of seats. American Airlines’ busiest routes to and from Chicago O’Hare International Airport by number of flights operated are shown in the table below.

Just like United Airlines, American Airlines’ busiest routes from Chicago O’Hare International Airport are primarily to the carrier’s other major hubs, such as Los Angeles International Airport, Philadelphia International Airport, and Miami International Airport. This allows the carrier to offer extensive onward connections to destinations across the world, with these three airports serving as American Airlines’ primary hubs for flights across the Pacific, to Europe, and to Central and South America, respectively.

Further Growth For United Airlines

Photo: MKPhoto12 | Shutterstock

Earlier this year, United Airlines was granted the use of six additional gates at Chicago O’Hare International Airport, allowing for further growth in the future. At the time, the carrier’s Chief Commercial Officer, Andrew Nocella, spoke about United Airlines’ strategy and upcoming growth at the airport. As reported at the time by The Points Guy, Nocella said that:

“Our current facilities are very full, and we know people want to fly in peak periods so these six gates will allow us to continue to execute on the United Next plan. We’ve been very consistent in our strategy here in Chicago, and as a result of that, we’ve got the six gates, and we’re going to continue to grow. We think the economics of the hub look really darn good right now.”

Although no major international expansion is planned, United Airlines is soon due to launch a couple of new domestic routes from Chicago O’Hare International Airport to Dayton International Airport (DAY) and Green Bay Austin Straubel International Airport (GRB).

That said, the carrier already serves several major international destinations from the airport, including London Heathrow Airport (LHR), Paris Charles de Gaulle Airport (CDG), Frankfurt Airport (FRA), and Tokyo Haneda Airport (HND). Curiously, United Airlines’ CEO, Scott Kirby, used to work at American Airlines, and so likely has a deep understanding of how both carriers work.

The Response From American Airlines

Photo: PlanespotterA320 | Wikimedia Commons

Following the COVID-19 pandemic, American Airlines’ recovery at Chicago O’Hare International Airport was much slower than that of United Airlines. Following the retirement of its Boeing 767-300s and Airbus A330-200s, delivery delays from Boeing of its 787s meant that the oneworld carrier simply did not have the aircraft available to grow, particularly on international services.

However, after several years of limited growth at the airport, American Airlines recently announced significant expansion, with a handful of new routes, including Curaçao International Airport (CUR), Querétaro Intercontinental Airport (QRO), Sint Maarten Princess Juliana International Airport (SXM), and St. Croix Henry E. Rohlsen Airport (STX).

The carrier is also set to resume several previously operated routes before the end of 2025, such as Honolulu Daniel K. Inouye International Airport (HNL), Mexico City International Airport (MEX), San José Juan Santamaría International Airport (SJO), and Guatemala City La Aurora International Airport (GUA).

Gate Usage Controversy

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American Airlines has been, understandably, not happy about United Airlines being awarded more operating gates at Chicago O’Hare International Airport, with the oneworld carrier filing a lawsuit against the city. With significant expansion and renovation planned at the airport over the coming years, as part of its so-called O’Hare 21 project, American Airlines wants to get a piece of the action. In a statement made to The Points Guy, the carrier said:

“American is committed to keeping O’Hare competitive, as our presence yields more extensive flight schedules for our Chicagoland customers and travelers from across the world, making the city a more desirable destination for business development. That’s why we’re rejecting the Chicago Department of Aviation’s (CDA) improper trigger of the reallocation of gates at O’Hare – it’s not only a violation of the agreement signed in 2018, but it stifles the competitive essence of the dual-hub by inhibiting our continued growth.”

Photo: Bo Shen | Shutterstock

This trend of dominance by United Airlines shows no sign of stopping anytime soon. In the short term at least, the Star Alliance carrier has been granted more operating gates at Chicago O’Hare International Airport, which means that its expansion is only likely to continue.

The airport’s O’Hare 21 expansion project will see further growth over the coming years, with two new concourses being added, in addition to further gates and lounges at the existing Terminals 2 and 5. A reorganization of the airport will also allow for more seamless transfers between international and domestic flights operated by both United Airlines and American Airlines.

The Airport’s Busiest International Routes

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Another way to compare the two airlines’ operations at Chicago O’Hare International Airport is by looking at the international routes operated, showcasing the airport on a global stage.

When it comes to the five busiest international routes from the airport (when measured by passenger numbers), United Airlines operates all five of them, while American Airlines only operates three. These routes are shown in the table above.

One Clear Winner

Photo: Ian Dewar Photography | Shutterstock

When looking at the figures, one carrier clearly dominates the operation at Chicago O’Hare International Airport. With a market share of 40%, United Airlines currently operates more than 35,000 flights per month, equating to more than four million seats on offer to passengers. By contrast, American Airlines will operate just 27,000 flights in the same timeframe, offering a total of just over three million seats.

While United Airlines will undoubtedly be pleased to be the dominant carrier at Chicago O’Hare International Airport, from a passenger perspective, such a monopoly does somewhat limit choice and risks an increase in fares. As American’s legal battle continues, it remains to be seen how any future gate allocations at Chicago O’Hare International Airport will be handled, and whether the carrier will get the chance to better compete against its Star Alliance rival. For now, the battle continues.

IATA Code

ORD

City

Chicago

Designation

Major-International