The escalated battle at Chicago O'Hare between United and American is likely to hurt the short-term bottom lines of both airlines.
Consumers, though, should win.
"Anytime airlines fight, there's one immediate winner: passengers," said Scott Keyes, founder of the subscription service Going, which helps travelers find bargain flights. "The single biggest driver of cheap flights isn't distance or city size; it's competition between airlines."
American surged its O'Hare flying last summer, but the competition has further intensified in the past month. After the pandemic, American built back more slowly than United at O'Hare, and now American is pushing to get back to pre-Covid volume.
American made a late-December announcement that its spring-break flying from Chicago will be up 30% on peak days.
Then came United's Q4 earnings call on Jan. 21, when CEO Scott Kirby said United would respond with more O'Hare flights. United did exactly that a week later with five announced regional routes that American already was flying.
"In 2026 we're drawing a line in the sand," Kirby declared during the call.
United now plans to fly as many as 750 flights on peak days at O'Hare this summer, an increase of 170 flights from last summer and about 100 more peak-day flights than it had previously planned.
Robert Isom
American plans to average 500 to 550 departures per day at O'Hare this summer, CEO Robert Isom said during the airline's Jan. 27 earnings call. That's about a 30% increase from two summers ago.
For Chicago flyers and those in the Midwest more generally, the airlines' large build-up will mean broad increases in connectivity. Along with 25 new O'Hare routes, United will offer either more flight frequencies or larger aircraft on routes to 80-plus cities from O'Hare this summer.
Meanwhile, American plans service increases to 75 destinations from Chicago this spring on top of 32 new routes it has announced since last February.
"This is great news for travelers to and from Chicago, because that added capacity will drive down fares," Keyes said.
An example of a city that benefits is Erie, Pa. American revealed plans on Dec. 18 to begin daily O'Hare-Erie service in May. A day later, United fired back, announcing O'Hare-Erie flights three times a day beginning in June.
There's also heightened competition at the front of planes, as American attempts to eat into United's substantial lead at O'Hare among premium flyers and United digs in to defend its advantage.
For instance, American last June debuted its Flagship Suite business-class seat on a Boeing 787-9 Dreamliner flying from O'Hare to London, while United has deployed many of its most modern narrowbodies, the Airbus A321neo, at O'Hare. The 200-seat plane has 20 first-class seats and 57 Economy Plus seats with extra legroom.
The turf war's cost
For both airlines, the O'Hare turf war could harm short-term profits. Kirby said that United made approximately $500 million in profit at O'Hare last year, a number he said that would have been closer to $600 million absent American's build-up at the airport beginning in the late spring.
Kirby also contended that American is losing loads of money at O'Hare. He estimated the airline lost $500 million last year and said that figure could double based on American's growth plans this year.
American has repeatedly declined to comment on its O'Hare bottom line. Pointedly, Isom focused his comments on the future when asked about it during the Jan. 27 earnings call.
"Chicago is strategically important. And at the end of the day, it's going to help overall system profitability, but we fully expect that Chicago will return to its position as one of our midlevel profitability hubs," he said.
What is clear is that United enjoys a large edge over American in Chicago. In terms of yield (revenue per passenger mile flown), United did 12.2% better than American in the second quarter of 2025, which is the most recent data released by the DOT.
United also said that its share of high-yielding corporate customers at O'Hare is 65%, compared to American's 27%.
American's reasoning for rebuilding its O'Hare operation, though, goes beyond immediate profits and losses, said Gary Leff, author of the View from the Wing blog.
Gary Leff
Drawing in more co-branded credit card revenue from the Chicago area, which is the country's second-largest business market, is one key consideration, Leff said. That credit card income doesn't show up in American's O'Hare-specific bottom line.
Plus, American has huge investments to protect at O'Hare, made over several decades.
"It's too big and too valuable to walk away from," Leff said.
Also at play is the key role O'Hare plays in American's broader network, which Isom talked about during American's Q4 earnings call.
American is strong across the south with its largest hub at Dallas-Fort Worth and hubs in Charlotte and Phoenix, but Chicago is its only midcontinent hub in the north.
"You can't really be an effective competitor in the Upper Midwest, the Plains or even the Pacific Northwest without a hub where you can effectively connect to the Northeast," said Brett Snyder, author of the Cranky Flier blog.
Still, neither Leff nor Snyder envision a path in the foreseeable future in which American catches United at O'Hare.
But can American eventually thrive at O'Hare in second place?
"That's the question," Snyder said.