Between July 2024 and June 2025, Seattle-Tacoma International Airport recorded an impressive total of 51.3 million two-way passengers. This significant traffic marks the airport’s ongoing growth as a major hub, with Alaska Airlines leading the pack, accounting for approximately 52% of the total passenger volume. Delta Air Lines followed in a strong second place, capturing nearly a quarter of the traffic.
During this twelve-month period, Seattle-Tacoma offered nonstop scheduled passenger flights to over 133 destinations globally, including 37 international locations. A notable development included the addition of several long-haul carriers, such as China Airlines in July 2024, STARLUX in August 2024, Philippine Airlines in October 2024, and SAS in May 2025. Additionally, Hawaiian Airlines launched its first long-haul service from Seattle in partnership with Alaska Airlines, further solidifying the airport’s role as a global transit hub.
Top Passenger Markets from Seattle
The analysis of passenger traffic reveals that Anchorage was the top market for the Seattle-Tacoma International Airport with 1.96 million round-trip passengers. Alaska Airlines facilitated 79% of these trips, while Delta accounted for 21%. A significant portion of Anchorage passengers, approximately 83%, connected to other flights via Seattle.
Seattle’s top ten markets by total passengers highlight the airport’s diverse traffic patterns, including both local and connecting passengers. For instance, while Los Angeles International was the second most trafficked route overall, with 1.95 million passengers, it emerged as the leading local market, where over 1.50 million travelers flew exclusively between Seattle and Los Angeles.
The following table illustrates the top passenger markets from Seattle, focusing on total passengers and local traffic:
Total Passengers* Seattle To/From… Load Factor** % Local***
1.96 million Anchorage 83% 17%
1.95 million Los Angeles Intl. 79% 77%
1.87 million Phoenix 84% 70%
1.80 million Denver 87% 53%
1.83 million Las Vegas 83% 71%
1.67 million Dallas/Fort Worth 88% 57%
1.59 million San Francisco 80% 69%
1.55 million Chicago O’Hare 89% 54%
1.20 million San Diego 82% 77%
1.10 million Portland 76% 14%
* July 2024-June 2025. US DOT
** Load Factor refers to the percentage of available seating capacity that is filled with passengers.
*** Local traffic refers to those who only flew to/from Seattle.
The market between Seattle and Los Angeles has become increasingly competitive, supported by the entry of new operators such as Frontier Airlines in December 2024. This development followed Spirit Airlines’ exit from the route in May 2025, which reduced the number of airlines operating that market from six to five.
International Destinations on the Rise
In terms of international travel, the Seattle-Taipei route surpassed Vancouver to become the top international market, with 650,000 round-trip passengers during the same period. This shift is attributed to Delta’s entry into the market in June 2024, along with the return of China Airlines and the launch of STARLUX. Together with EVA Air, these carriers now provide a record four airlines servicing the Seattle-Taipei route, with up to five daily flights available.
The evolving landscape of air travel at Seattle-Tacoma International Airport underscores its importance as a key player in the aviation sector, with expanding routes and growing passenger numbers reflecting the airport’s ambition to establish itself as a global hub.
