Mubboo Flight Route Structure Index 2026: Most Growth on International Air Routes Came From Airlines Already Flying Them
CHEYENNE, Wyo. – October 8, 2026 – On most international air routes that grew between 2024 and 2025, the extra seats came from airlines that were already flying them, according to the Mubboo Flight Route Structure Index 2026, published by Mubboo Flights Research. No new airline appeared on 151 of 234 growing US-linked routes, 42 of 51 growing Australian routes and 15 of 27 growing Brazilian routes. Measured in seats rather than routes, airlines already on a route supplied 84% of all the seats added on US-linked routes, 83% in Australia and 94% in Brazil.
The index is built from airline-level capacity records published by the US Bureau of Transportation Statistics, Australia's BITRE, Brazil's ANAC and Taiwan's Civil Aeronautics Administration. It reports three measurements separately and does not combine them into a ranking: how much capacity arrived, who controlled it once documented airline groups and authorised joint businesses are combined, and whether a second meaningful option was present in every month rather than only across the year.
The gap is widest on the busiest routes
Five airlines fly New York JFK to London Heathrow, carrying virtually all of its 3.9 million seats in 2025. Counted by airline, the route reads as 3.68 evenly matched operators. But four of those five sit inside two joint businesses that hold antitrust immunity from the US Department of Transportation — American with British Airways under Order 2010-7-8, and Delta with Virgin Atlantic under Order 2013-9-14 — and together they hold 94.88% of the seats. Treat each pair as the single commercial decision its immunity permits, and the same capacity reads as 2.15 operators. JetBlue, with 5.11%, is the only independent carrier of any size.
Across the US panel, 447 routes carrying 88 million seats in 2025 fall inside a transatlantic joint business holding US antitrust immunity.
A second option is not always there every month
The third measure, continuity, separates the markets most. Of 427 US routes that had a second airline above 5% of seats across 2025, 170 did not have one in every month. The comparable Taiwanese figure is 8 of 77. The study attributes the US gap to a network with heavy seasonal leisure flying rather than to anything about competition.
"Counting airline names on a route is not the same as counting independent sources of capacity, and neither is the same as counting the months a second option is actually there," said Richard Lee, founder of Mubboo, who leads Mubboo Flights Research. "None of that means these arrangements harmed anyone — regulators approved them, and in one case said it would likely put downward pressure on fares. It means the industry reports one number where there are three."
The study measures capacity, not prices. It makes no claim about airfares, consumer welfare or competition law, does not rank countries or routes globally, and labels its corporate-group and joint-business adjustments as incomplete scenarios published beside the raw airline counts rather than instead of them. It covers four markets because those are the ones whose regulators publish airline-level route capacity at all.
A 95-second video summary explains the three measurements with the New York–London, Brisbane–Doha and US monthly examples.
Data and resources
Full report, methodology and every chart: https://mubboo.flights/research/flight-route-structure-index
All 3,656 routes (CSV): https://mubboo.flights/research/flight-route-structure-index/data/mubboo-flight-route-structure-index-2026-routes.csv
Media kit (one ZIP with a one-page summary, citations, every chart as SVG and PNG, and the data): https://mubboo.flights/research/flight-route-structure-index/media-kit.zip
Permanent, versioned data archive: https://doi.org/10.5281/zenodo.22995092
The report is also published in Portuguese and Traditional Chinese, linked from the report page.
Charts and data are published under CC BY 4.0: they may be reused, including commercially, with credit to "Mubboo Flights Research" and a link to the report.
About Mubboo Flights
Mubboo Flights is a flight comparison service operated by Mubboo LLC, a limited liability company registered in Wyoming, United States. It compares flights from more than 800 airlines and also covers hotels, car rentals and more than 400,000 tours, tickets and activities worldwide, with virtual drives and walks that let travelers preview a city before they book. Its research arm, Mubboo Flights Research, publishes original aviation studies. Mubboo Research reports: https://mubboo.flights/research