Chicago O’Hare (ORD) is the most connected U.S. domestic megahub in OAG’s 2026 scheduled-connection ranking. That is a measure of potential connections—not passenger volume. The Federal Aviation Administration’s forecast estimates more 2025 enplanements at Atlanta and Dallas/Fort Worth than at O’Hare.
What “dominant hub” means for O’Hare
“Hub” can describe different things. The FAA assigns airport hub-size categories according to an airport’s share of total U.S. passenger enplanements; those categories are used in federal airport planning and funding. OAG’s megahub ranking instead compares the potential for scheduled passenger connections relative to destinations served. An airline hub is a carrier’s network structure for connecting passengers. These measures are related, but they are not interchangeable.
For this article, O’Hare’s dominance means that it ranks first among U.S. domestic megahubs by OAG’s 2026 scheduled-connectivity measure. OAG’s ranking is based on the busiest day for global aviation in the year to August 2026: Sunday, August 2. The ranking is a snapshot of schedules, which can change with the season; it does not guarantee that every theoretical connection is available or practical for a traveler.
How O’Hare compares with Atlanta and Dallas/Fort Worth
OAG’s 2026 ranking places O’Hare first among the U.S. domestic megahubs it compares. Atlanta (ATL) ranks second and Dallas/Fort Worth (DFW) third.
| Measure | O’Hare (ORD) | Atlanta (ATL) | Dallas/Fort Worth (DFW) |
|---|---|---|---|
| OAG 2026 U.S. domestic megahub rank | 1st | 2nd | 3rd |
| OAG connectivity index, 2026 | 368.5 | 319.3 | 242.0 |
| OAG dominant carrier share of flights, 2026 | United: 49% | Delta: 80% | American: 85% |
| FAA estimated 2025 enplanements, FY 2025–2055 forecast | 40.2 million | 52.1 million | 41.6 million |
OAG’s U.S. ranking selects 25 airports with the highest ratio of possible scheduled connections to destinations served. The ranking page reports index values but does not fully establish the index’s weighting or technical limitations, so the scores are best treated as a comparative ranking measure rather than a count of travelers or completed trips. OAG’s 2026 Megahubs ranking.
The passenger figures tell a different story. The FAA forecast estimates 2025 enplanements of 52.1 million at Atlanta, 41.6 million at DFW and 40.2 million at O’Hare. These are forecast estimates, not final observed totals; the FAA projects Atlanta to remain the busiest airport by enplanements through the forecast period. FAA, Forecast FY 2025–2055.
Rank #2
Why O’Hare ranks first for scheduled connections
A broad set of destinations and potential connections
OAG reports 227 domestic destinations for O’Hare and 83,647 potential connections on its busiest day in the 2026 comparison. It also reports that domestic destinations increased from 214 to 227 and capacity grew 12% that year. These are schedule-based figures for the comparison, not a promise of 83,647 bookable itineraries on an ordinary day.
The practical mechanism is straightforward: a hub can connect passengers arriving from one destination with flights departing for many others. A larger set of scheduled destinations creates more possible combinations, and OAG’s measure evaluates those possibilities relative to destinations served. O’Hare’s leading score indicates that its schedule offered the strongest connection potential among the U.S. airports in this comparison.
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United is O’Hare’s dominant carrier in OAG’s snapshot, accounting for 49% of flights. That is a substantial presence, but a smaller share than Delta’s 80% at Atlanta or American’s 85% at DFW. On this comparison, O’Hare’s schedule is more distributed across carriers than those two airports; that does not mean the carriers share the airport evenly.
Capacity expansion is context, not proof of the cause
Chicago has pursued capacity improvements through its O’Hare 21 program, including planned concourses and terminal work, as described by the Chicago Department of Aviation. That investment is relevant context, but the available ranking and city announcement do not isolate how much geography, airline scheduling, runway layout or construction contributed to O’Hare’s first-place result. It would overstate the evidence to credit any one factor as the cause.
Rank #4
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Is O’Hare the busiest airport in the United States?
Not by the FAA’s cited 2025 enplanement forecast. Atlanta is estimated at 52.1 million enplanements, compared with 40.2 million at O’Hare; DFW is also ahead at 41.6 million. The forecast additionally places Denver at 39.9 million and Los Angeles at 36.9 million. Because these are forecast estimates, they should not be presented as final passenger totals.
Enplanements count passenger boardings, not the number of possible connecting combinations. The FAA says its boarding data is collected by calendar year and used to calculate airport categories and entitlements for a later fiscal year. Its hub-size categories are based on total calendar-year enplanements. The FAA page says CY 2025 ranking data was updated September 24, 2026, and final CY 2026 data will be available in late August 2027. FAA passenger and enplanement data.
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In a September 10, 2024 announcement, the Chicago Department of Aviation said O’Hare ranked first in the United States and ninth globally in OAG’s 2024 Megahubs Index. The department also reported that O’Hare had consistently ranked first on OAG’s Top 25 U.S. Domestic Airport Megahubs report since publication began in 2017, except in 2020 and 2021, when reports were not issued. That history is the city department’s account of OAG’s rankings; OAG’s 2026 page is the current source for the latest U.S. domestic result. Chicago Department of Aviation, September 10, 2024.
Mayor Brandon Johnson said: “O’Hare is not just Chicago’s airport; it is the world’s airport,” in the department’s 2024 release. CDA Commissioner Jamie Rhee said: “O’Hare’s leadership in connectivity is the result of strategic planning, a commitment to public safety, strong airline partnerships, and a relentless focus on innovation,” in the same release. These are city officials’ perspectives, not independent evidence of what caused the ranking.
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