Revealed: The US's Top 10 Busiest International Routes

Between August 2024 and July 2025, 257 million passengers flew internationally to/from the US. Over 700,000 people did so daily. Traffic was 2% higher than for the 12 months to July 2024 and 6% higher than for the year to July 2019, before the pandemic struck. These findings are from examining all international routes using Department of Transportation data.

Returning to the August 2024 to July 2025 period, over 100 scheduled carriers operated. United Airlines was number one (37.7 million passengers), followed by American (37.6 million), Delta Air Lines (29.3 million), Air Canada (11.9 million), and JetBlue (11.0 million).

The US’s Top 10 International Airport Pairs

The following analysis looks at airport pairs—not city pairs. The results are therefore necessarily a bit different from what they might otherwise be. Some readers might not like it. While informative in itself, it is, in some cases, only part of the overall picture.

Passenger traffic includes everyone who traveled between the two airports. It does not just reflect the local or point-to-point market, whether they flew nonstop or connected en route to secure lower fares or otherwise. It also includes those who transited to another flight at either or both ends of the route.

For example, 3.18 million round-trip passengers flew between New York JFK and London Heathrow. This was, of course, number one. It always will be. They are the world’s top two airports for long-haul activity.

Having so much traffic is partly because the local market is enormous: it had 1.81 million passengers. But it is also because many people—about 1.37 million—transited to another flight at Heathrow or JFK or both. It is these factors combined that explain why Cirium Diio shows it had an average of 21 daily services.

Traffic Has Declined Between San Francisco & Taipei

This long airport pair covers 5,621 nautical miles (10,410 km) each way. With 1.27 million passengers, it was the US’s leading Asian market on an airport pair basis. However, it would not be first at the city level.

San Francisco traffic to/from Taipei Taoyuan has declined recently. The US DOT shows that passenger volume fell by 5% compared to the year to July 2024. Some 72,000 fewer passengers were carried. Despite this, the carriers had 4% more seats for sale. As such, the overall seat load factor necessarily fell—from 85% to 77%. It was the joint-lowest of the top 10 airport pairs. Yields likely fell, too.

STARLUX entered the market in December 2023 and has since captured 13% of the traffic. Its launch contributed to EVA Air’s traffic falling by 12% and China Airlines’ volume reducing by 27%. Both airlines’ capacity was reduced, but just not enough for the lower traffic. As such, their load factors fell by about ten points each in a year.

Dallas/Fort Worth To Cancun Explored

When local and transit traffic are combined, this airport pair had 1.09 million passengers. It was the US’s second most-trafficked market to/from Mexico. The US DOT shows that American had 76% of the market, with Dallas/Fort Worth being the country’s second-busiest airline hub. Spirit was second with 13%, followed by Sun Country with 6% and Frontier with 5%.

American transported about 828,000 passengers, of which an estimated 550,000 transited to another flight at its Texas hub. Cancun-Las Vegas, Portland (Oregon), Sacramento, Omaha, and London Heathrow were the five most popular origins and destinations. Obviously, this traffic played a critical role in helping American to fill 89% of seats on this route. In contrast, the other carriers—which rely on the local traffic—only filled between 74% and 78%.