The two leading airlines serving Seattle-Tacoma International Airport (Sea-Tac), Alaska and Delta airlines, together served more than 70% of the passengers flying via Sea-Tac last year ― with Alaska holding a commanding market share in domestic air service, at 52.1%, while Delta dominates international service, with a 31.3% market share.
The next closest airlines in terms of the overall passenger market share in 2018, among some 32 airlines serving Sea-Tac, are United, 6.4%; Southwest, 6.4%; and American, 5.2%, according to figures prepared for Seattle Business magazine by Sea-Tac.
“Sea-Tac is one of just seven airports in the U.S. with more than one airline operating a true connecting hub,” says Perry Cooper, spokesperson for Sea-Tac. “As a result of this, travelers looking to go to destinations as close as Pasco and as far as Tokyo have multiple carriers and multiple flight schedules to choose from.”
The growth of Alaska and Delta ― the two dominate airlines serving Sea-Tac ― over the past decade, however, is the real story. Between 2009 and 2018, Alaska’s overall Sea-Tac passenger count has jumped 61%, from 15 million to 24.1 million. Delta’s overall passenger growth at Sea-Tac over the period skyrocketed sixfold, from 1.9 million to 11.5 million passengers served.
Delta’s international-service growth at Sea-Tac is particularly impressive. Delta wasn’t even ranked among the top 10 Airlines providing international service at Sea-Tac in 2009, according to Sea-Tac figures, while Alaska ranked first, with 953,193 international passengers served that year and a 36.2% market share. Last year, Delta ranked first, with 1.7 million international passengers served and a 31.3% market share ― followed by Alaska, down slightly from 2009 at 934,564 international passengers served, or 17.2% of the market.
Delta’s jump into the lead in international-passenger service at Sea-Tac was aided in a major way by its acquisition of the former Northwest Airlines a decade ago. Northwest in 2009 ranked No. 2 at Sea-Tac for international passengers served, with a 14.4% market share at the time.
Delta’s ascendance to dominance in the international-flight sector at Sea-Tac also came during a period of increasing competition in that area, with 11 new international airlines added to Sea-Tac’s roster since 2016. Domestic passenger service at Sea-Tac also has exploded in recent years.
“Since 2014, we have grown from 82 nonstop domestic destinations to 91, and average daily domestic departures from 396 to 530,” Cooper says.
Between 2009 and 2018, Delta also jumped from being the No. 5 carrier on the domestic-passenger front at Sea-Tac, with 1.9 million passengers served and a 6.6% market share, to the No. 2 slot last year, with 9.8 million passengers served and a 22.1% market share.
The growth of Alaska and Delta at Sea Tac is set against a backdrop of explosive passenger growth at the airport overall, adding credence to the cliché that a rising tide raises all boats. Over the five-year period ending in 2018, commercial airline passenger traffic at Sea-Tac jumped from 34.8 million to 49.8 million flyers ― a 43% increase. The Port of Seattle projects the annual passenger count at 66 million by 2034.
Airlines Ranked by Overall Sea-Tac Passenger Traffic in 2018
- Alaska Airlines, 24.1M
- Delta Air Lines, 11.5M
- United Airlines, 3.2M
- Southwest Airlines, 3.2M
- American Airlines, 2.6M