Summary
- The Big Three airlines in the US have minuscule overlap on domestic routes.
- Out of 4,300+ September routes, the trio compete head-to-head on just 22.
- American Airlines is the largest airline of the three in just one of them.
American Airlines
,
Delta Air Lines
, and
United Airlines
are known as the US Big Three. They are the three largest carriers by flights, available seat miles, and various other measures. Using OAG data to examine the trio’s network in September 2024 shows 4,300+ domestic routes. However, going through them indicates that all three airlines compete head-to-head on 22.
The 22 overlapping routes in September
It is not surprising that the degree of domestic overlap is tiny. After all, American, Delta, and United generally have very different hubs, reducing the likelihood of direct competition. Indeed, they’re naturally more likely to see each other when they jointly have a hub or at a major airport with flights from another hub.
All 22 routes involve Chicago O’Hare and Los Angeles International. Funnily enough, O’Hare-Los Angeles isn’t one of the routes, as Delta does not serve it.
As everyone knows, Chicagoland and the LA Basin are massively populous. More than this, O’Hare is a hub for America and United, while Los Angeles International is a hub for all three carriers. However, as Los Angeles is generally not among their top hubs and is so well-served by other operators, the trio collectively has fewer than half of its flights (49%).
As always, the results might differ in other months and certainly at the city level. While other airlines serve many of the 22 airport pairs, this article is only interested in American, Delta, and United. The stated % of flights refers to only the number one airline of the three operators—not the whole market.
- Chicago O’Hare-Atlanta (Delta is first of the three airlines; 49.1% of September flights)
- Chicago O’Hare-Detroit (United is top; 38.6%)
- Chicago O’Hare-Boston (United is number one; 41.2%)
- Chicago O’Hare-Minneapolis (United is first; 44.0%)
- Chicago O’Hare-New York LaGuardia (United is top; 49.0%)
- Chicago O’Hare-Salt Lake City (United is number one; 35.2%)
- Chicago O’Hare-Seattle (United is first; 47.2%)
- Los Angeles-Austin (Delta is top; 45.6%)
- Los Angeles-Boston (Delta is number one; 38.5%)
- Los Angeles-Denver (United is first; 60.7%)
- Los Angeles-Houston Intercontinental (United is top; 78.7%)
- Los Angeles-Honolulu (all three airlines have triple-daily flights, so there is no leader in this sense)
- Los Angeles-Kahului (all three airlines have a daily flight, so there is no leader in this sense)
- Los Angeles-Kona (all three airlines have a daily flight, so there is no leader in this sense)
- Los Angeles-Las Vegas (Delta is first; 38.1%)
- Los Angeles-Lihue (all three airlines have a daily flight, so there is no leader in this sense)
- Los Angeles-Orlando (Delta is top; 50.2%)
- Los Angeles-Phoenix (American is number one; 44.1%)
- Los Angeles-Reno (Delta is first; 55.0%)
- Los Angeles-Sacramento (Delta is top; 58.7%)
- Los Angeles-San Francisco (United is number one; 44.7%)
- Los Angeles-Seattle (United is first; 61.9%)
Image: GCMap
American is first only once
Surprisingly or not, American is the leading operator on only one airport pair where it competes directly with Delta and United. It is from Los Angeles to the ex-US Airways hub of Phoenix. The trio has 408 one-way flights in September, with 12 to 14 daily flights each way. (Frontier and Southwest also serve the airport pair but are not considered here.)
Photo: Wenjie Zheng | Shutterstock
American has 180 of the 408 flights—44.1% of the threesome’s total—all on mainline equipment. That’s unsurprising given that it has a hub on both ends and is a significant market for point-to-point travel (800,000+ passengers last year). There are usually six daily departures, with the A321ceo being the leading variant, followed by the 737-800, A321neo, and A319. Delta Connection has 138 one-way flights, and United has 90 (some being on United Express aircraft).