Seattle breaks another passenger record amid Delta-Alaska turf war

Ben Mutzabaugh | USA TODAY

Business is booming at Seattle-Tacoma International Airport, which broke its all-time monthly passenger record in June.

The airport counted 4,011,247 passengers for the month of June, a 12% jump over the same month a year ago and the first-time ever that the airport has topped the 4 million mark in a single month.

But the record is becoming old hat for Sea-Tac. The airport has now set a string of both monthly and annual records amid an ongoing turf war between Seattle-based Alaska Airlines and Delta Air Lines. The airport says if the current trends continue, it expects a fourth-consecutive annual record for total passengers.

Sea-Tac's previous record for one month came in August of 2014, when 3,968,007 fliers used the airport. The airport says the summer season is traditionally its busiest, with the highest passenger numbers typically coming in August "followed by July and June." So far in 2015, Sea-Tac's passenger traffic is up 13.1% over the same period last year, including a 15.7% rise for international passengers.

The growth has made Sea-Tac one of the fastest growing major airports in the world.

It all comes amid a pitched market-share battle between Alaska Air and Delta, which – for now – continue to remain partners. But that partnership has endured considerable strain since 2012.

Alaska Air is based in Seattle and has long been the airport's top carrier. Delta, however, began expanding its Seattle operation in 2012, using its passenger-sharing partnership with Alaska Air to funnel domestic passengers to its newly launched international flights, including several to Asia.

But Delta has since expanded that effort, turning Sea-Tac into a full-fledged hub for both international and domestic flights. In doing so, Delta has fleshed a domestic network that goes head-to-head with Alaska on its home turf. Many of Delta's new Seattle routes have even come on routes that are among Alaska Air's most prized, such as nonstops between Seattle and cities in the Pacific Northwest and Alaska .

Delta's other recently added Seattle flights include nonstops to Portland, Ore., and Los Angeles. Portland is Alaska Air's second-biggest hub while Los Angeles is one of Alaska Air's focus cities.

The stepped up competition has created an escalating rivalry between the two.

Alaska Air has looked to defend its position in Seattle, adding dozens of new routes within the U.S. – and some to Mexico – as it tries to cement its position as the city's busiest carrier.

Beyond Seattle, Alaska even has gone so far as to add several nonstop routes from Salt Lake City. Alaska Air previously had little presence at that Utah airport, but it is a hub for Delta. The move was widely viewed as retaliation against Delta, though Alaska Air has downplayed such suggestions.

For Seattle customers, however, the competition has led to a bonanza of new flights, frequent fare sales and a slew of special offers for frequent-flier.

The "battle for Seattle" also has boosted Sea-Tac's image abroad, according to the Puget Sound Business Journal.

John Grant, executive vice president of airline data and schedule provider OAG, tells the publication that the turf war is increasingly putting Seattle on the itineraries of overseas passengers. Delta is routing its own connecting passengers through the hub, of course. But Alaska Air -- which has a broad list of frequent-flier partners -- has been cultivating new partnerships through which it can funnel its U.S. customers to the international flights of partners.

"If the market was as it was 18 months ago, when Delta and Alaska were working very closely, those overseas Asian carriers would have found it very difficult to get an arrangement with Alaska Airlines," Grant says to the Business Journal. "Now that relationship isn't as strong as it used to be, and on that basis that will enable them to see more opportunities, and Alaska will work with those airlines as well."