The airport's original control tower, built in the 1950s, is now located in the airport's passenger terminal and used as a ramp control tower, after being repaired from damages caused by the Nisqually earthquake in 2001.A recurring problem at the airport is misidentification of the westernmost taxiway, Taxiway Tango, as a runway.

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The airport was built by the Port of Seattle in 1944 after the U. military took control of Boeing Field in World War II.

The Port received $1 million from the Civil Aeronautics Administration to build the airport and $100,000 from the City of Tacoma.

In the late 1980s the Port of Seattle and a council representing local county governments considered the future of air traffic in the region and predicted that airport could reach capacity by 2000.

The planning committee concluded in 1992 that the best solution was to add a third runway to the airport and construct a supplemental two-runway airport in one of the neighboring counties.

The airport has flights to cities throughout North America, Europe, the Middle East and Asia.

It is the main hub for Alaska Airlines and its regional subsidiary Horizon Air, whose headquarters are near the airport.In 1973, -million new terminal was built over and around the 1949 structure; the new terminal quadrupled the area for public use. Senator Henry Martin "Scoop" Jackson in 1983, the Seattle Port Commission voted to change the name of the airport to Henry M. Denizens of Tacoma interpreted the change as an insult to their community—the second time in the airport's history that the port authorities had attempted to remove "Tacoma" from the name.Residents of the surrounding area filed lawsuits against the Port in the early 1970s, complaining of noise, vibration, smoke and other problems. The 0,000 that Tacoma had provided for the airport's construction during World War II had come with an explicit promise that the city would be included in the airport's name.In 1966 Scandinavian Airlines began the airport's first non-stop route to mainland Europe (Pan Am nonstops to London began around 1961). The two-story North Concourse (later dubbed Concourse D) added four gate positions and a new wing 600 feet (180 m) long and 30 feet (9.1 m) wide.and lasting from 1967 to 1973, adding a second runway, a parking garage, two satellite terminals and other improvements.It is a hub and international gateway to Asia and Europe for Delta Air Lines, which has expanded at Sea–Tac since 2011.