Seattle–Tacoma International Airport

Construction and early growth (1942–1967)

A shared public airport was proposed by the Port of Seattle and Port of Tacoma in the late 1920s, but deferred plans after the legality of public ports operating such facilities was rejected by the state attorney general in a published opinion. The state legislature authorized municipal corporations such as public ports to establish aviation facilities in 1941.^[8] The Port of Seattle accepted a $1 million grant (equivalent to $14.7 million in 2023 dollars)^[9] from the Civil Aeronautics Administration in March 1942 to construct a new airport to serve the Seattle area after the U.S. military took control of Boeing Field during World War II. A site on U.S. Route 99 near Bow Lake south of Seattle was chosen at the end of the month ahead of another candidate near Lake Sammamish that was considered too close to the Cascade Range. The City of Tacoma provided $100,000 towards the airport's construction costs as part of a deal for the Bow Lake site, centered around an existing private airfield plagued by heavy fog.^[10] Construction of the airport, which was named Seattle–Tacoma in recognition of Tacoma's contribution, began with a groundbreaking ceremony on January 2, 1943.^[11][12]

The project was originally estimated to cost $1.7 million (equivalent to $23.4 million in 2023 dollars),^[9] but the sandy soil conditions drove the final construction price to over $4.2 million (equivalent to $57.8 million in 2023 dollars).^[9] The airport's plateau was formed through 6.5 million cubic yards (5,000,000 m³) of excavated earth.^[10] A proposal to rename the airport for Boeing president Philip G. Johnson shortly after his death in September 1944 was rejected by Port of Seattle commissioners due to the objections of Tacoma. The first ceremonial landing at Seattle–Tacoma Airport was made on October 31, 1944, by a United Air Lines DC-3 carrying local elected officials and civic leaders.^[13] The first commercial flights launched in May 1945 with Northwest Airlines, but use was limited due to the U.S. Army Air Force's need for the airport to stage Boeing B-29 bombers for delivery. Various airlines had irregular flights to the airport, which used a Quonset hut with limited heating as a terminal until a permanent building was financed by a bond issue that voters approved in 1946.^[10]

The first scheduled commercial flights began on September 1, 1947, with Northwest Airlines and Western Airlines operating ten daily departures.^[14] They were joined by United, Alaska, Trans-Canada, Western, and Pan Am by 1951 as airlines departed from Boeing Field.^[15] The terminal at the renamed Seattle–Tacoma International Airport was formally dedicated by Governor Arthur Langlie on July 9, 1949, in front of a crowd of 30,000 spectators.^[16] The 71,000-square-foot (6,600 m²) building, designed by architect Herman A. Moldenhour, included a rooftop control tower and glass courting walls in the concourses.^[10][17] The 907-acre (367 ha) airport originally had four runways at 45-degree angles, between 5,000 and 6,100 feet (1,500 and 1,900 m) long, for crosswind operations. The two perpendicular runways were arranged into an "X"-shape that intersected near the longest, north–south runway; an additional runway to the south ran east–west.^[18] The terminal building's "inverted V" shape was arranged to match the runway layout.^[19] The north–south runway (now Runway 16L/34R)^[20] was lengthened to 7,500 ft (2,300 m) in 1950, to 8,500 ft (2,600 m) in 1955, and to 10,200 ft (3,100 m) in 1958 to support commercial jetliners.^[12][21]

The first parking lot at Sea–Tac opened in 1955 with room for 527 vehicles.^[18] The United States Postal Service opened its air mail terminal at the airport in 1957 to serve areas west of the Mississippi River and mail bound for Asia;^[18] other government agencies, including the Weather Bureau and the Customs Service also established offices at Sea–Tac. On June 28, 1959, Japan Airlines became the first international carrier to operate at Sea–Tac when it began its service to Tokyo.^[21] Several projects were completed by 1961 to prepare for the Seattle World's Fair the following year, including a runway extension over South 188th Street, which was placed in an automobile tunnel that opened in July 1961.^[22][23] During construction of the runway extension in February 1961, the fossilized skeleton of a Megalonyx jeffersonii giant sloth was discovered and excavated for display at the Burke Museum in Seattle.^[24] The two-story North Concourse (later named Concourse D)^[25] opened a month later with four gate positions to prepare for regular jetliner service; the concourse's wing was 600 feet (180 m) long and 30 feet (9.1 m) wide.^[26] Jetliner service began in October with Pan Am's Boeing 707 to Honolulu.^[15] The 688-foot-long (210 m) South Concourse (now Concourse A)^[25] opened in May 1961 alongside an expanded parking lot with capacity for 2,000 vehicles.^[15][27]

The 800-foot (240 m) long Concourse B opened in December 1964. It added eight gate positions, bringing the total to 19, a 12,000 square feet (1,100 m²) area housing international arrivals and the offices of U.S. Customs, Immigration, Public Health and the Department of Agriculture.^[26] Concourse C opened in July 1966.^[26] Four years later, it was extended to include another 10 gates, bringing the total to 35.^[26] The first non-stop flights from Sea–Tac to mainland Europe began in September 1966 with Scandinavian Airlines, who used a polar route to reach Copenhagen.^[15] A parallel second runway was completed 800 feet (240 m) west of the main runway in 1970.^[22]

Later expansions and third runway (1967–2008)

The Port embarked on a major expansion plan, designed by The Richardson Associates^[28] and lasting from 1967 to 1973, adding a second runway, a parking garage, two satellite terminals and other improvements. In 1973, $28 million new terminal was built over and around the 1949 structure;^[22] the new terminal quadrupled the area for public use.^[26][29] On July 1, 1973, the airport opened two new satellite terminals, along with an underground train system to connect them to the Main Terminal.^[29][30] These fully automatic shuttle trains were among the first of their kind in the United States. Also unprecedented in any U.S. airport: as part of the expansion the Port commissioned $300,000 worth of artworks; these were the start of what would become a large public art collection owned by the Port.^[29]

In the mid-1980s, the Main Terminal was renovated and another 150 feet (46 m) was added to the north end.^[26] Concourse D was expanded in 1987 with a rotunda that added four new gates.^[26] In 1993, Concourses B, C, and D were renovated. The project, designed by NBBJ, included the addition of 150,000 square feet (14,000 m²) and the renovation of 170,000 square feet (16,000 m²) of space in Concourses B, C, and D.^[31] On June 15, 2004, the 2,102-foot (641 m) new Concourse A was unveiled with 14 new gates, a dozen new restaurants, new artwork and the airport's first moving sidewalks.^[26]

Residents of the surrounding area filed lawsuits against the Port in the early 1970s, complaining of noise, vibration, smoke, and other problems. The Port and the government of King County adopted the Sea–Tac Communities Plan in 1976 to address problems and guide future development. The Port spent more than $100 million over the next decade to buy homes and school buildings in the vicinity, and soundproof others nearby. In the mid-1980s, the airport participated in the airport noise-compatibility program initiated by Congress in 1979. Airport-noise contours were developed, real estate was purchased and some homes were retrofitted to achieve noise mitigation.^[32]

In 1978 the U.S. ended airline regulation, and the U.S. airlines were allowed to determine routes and fares without government approval. Deregulation resulted in some new service to Seattle, including from TWA, then the fourth-largest U.S. airline, as well as Delta, National, and American.

Shortly after the death of U.S. Senator Henry Martin "Scoop" Jackson, the Port Commission voted on September 13, 1983, to change the airport's name to the Henry M. Jackson International Airport. Citizens of Tacoma were angered by the removal of their city's name despite their contribution to the airport's original construction budget, which had come with a promise to share the name. An additional complicating factor was the existence of another Jackson International Airport (now Jackson–Medgar Wiley Evers International Airport) in Jackson, Mississippi.^[33] During the November 1983 elections, an advisory referendum in Tacoma on the airport's name endorsed the original name by a 4–1 margin and two incumbent Port commissioners were defeated by candidates in favor of restoring the Sea–Tac name.^[33][34] Helen Jackson, the widow of the late senator, expressed her desire that their family remain neutral in the debate.^[35] With a 3–2 vote of the Port Commission on February 28, 1984, the name reverted to Seattle–Tacoma International Airport and the four signs with Jackson's name were removed.^[34][36]

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 the airport could reach capacity by 2000. The rising use of regional airliners such as Horizon Air caused aircraft movements to triple from 1978 to 1990 and air cargo use at the airport had also risen dramatically.^[37] In 1992, the planning committee concluded 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. Members of the community opposed a third runway, as did the Highline School District and the cities of Des Moines, Burien, Federal Way, Tukwila, and Normandy Park,^[38] but a 1994 study concluded there were no feasible sites for an additional airport. The Port of Seattle approved a plan for the new runway in 1996, prompting a lawsuit from opponents. The Port secured the necessary permits by agreeing to noise reduction programs and environmental protections.^[39] Runway opponents appealed these permits, but dropped their challenges in 2004.^[40]

The third runway, measuring 8,500 feet (2,600 m) long, opened on November 20, 2008, with a construction cost of $1.1 billion. Parallel to the existing two, the new runway is 2,500 ft (760 m) west of runway 34R, allowing landings on both in times of low visibility. The older runways are 800 ft (240 m) apart, too close to allow use of both in low visibility.^[41] The third runway project included 13 million cubic yards (9,900,000 m³) of fill dirt and several retaining walls, the longest of which is 1,430 feet (440 m) long and 130 feet (40 m) tall.^[42]

Modernization and expansion (2008–present)

The airport's Central Terminal building was renovated and expanded in 2003 in a project designed by Curtis W. Fentress, of Fentress Architects.^{[citation needed]} The renovation and expansion began in 1996 and underwent extensive modifications to accommodate new security requirements following the September 11 attacks in 2001.^[43]

In 2014, Delta Air Lines announced plans to expand Seattle into a transpacific hub. Since then, Delta has added numerous international flights and dozens of domestic flights to feed those services. Delta's increased presence in Seattle has been seen by some industry analysts as a response to United Airlines' transpacific hub at San Francisco, as well as Delta's disenchantment with its former Tokyo–Narita hub.^[44]

In late 2021, shortly after Alaska Airlines joined American Airlines in the Oneworld alliance, American announced that they would increase their international presence in Seattle.^[45] However, as of 2023, American had abandoned plans for long-haul flights to Asia from Seattle (including its proposed service to Bangalore, India) and ended service to London-Heathrow, their only intercontinental service from Seattle.^[46]

The North Satellite Terminal only received limited upgrades since it opened in 1973, and needed modernization.^[47] The Port of Seattle initially looked at simply updating the terminal in a project it called the North Satellite Renovation Plan (NorthSTAR). In 2016, the Port announced it would also significantly expand the terminal. The $550 million project called the North Satellite Modernization increased the size of the North Satellite by 201,000 square feet (18,700 m²)^[48] and another eight gates, bringing the total to 20. The project's first phase, dedicated on July 11, 2019, expanded the terminal to the west by 240 feet (73 m) and added eight gates, a mezzanine level with eateries, and a rooftop lounge for Alaska Airlines. The second phase modernized the remaining areas of the old terminal and expands dining and retail space around the twenty existing gates. The new terminal opened on June 29, 2021.^[49][50]

In 2022, the Port of Seattle completed a new 450,000-square-foot (42,000 m²) International Arrivals Facility (IAF) east of Concourse A, along with a 900-foot (270 m)-long high bridge that will take passengers from the South Satellite, up 85 feet (26 m) above the existing taxiway and over the top of Concourse A.^[51] The project was initially expected to be completed by 2021 at a cost of $766 million,^[52][53] though revised to $968 million in late 2018.^[54] The old customs and immigration facility was located in the basement of the South Satellite, and operated well over its design capacity. Additionally, the process for passengers was complicated by the satellite's isolated location.^[55] With the opening of the new IAF, Concourse A will now also be used for arriving international flights, nearly doubling the number of gates capable of serving arriving international passengers. The South Satellite Terminal is also planned to be renovated.^[48] The IAF was initially designed to accommodate 20 widebody aircraft, but four gates were not built to those specifications; the discrepancy was described as a "design flaw" by the Port of Seattle and blamed on the project's contractor.^[56]

The airport's digital infrastructure, including its website, phone lines, check-in system, and automated baggage sorting, was disabled by a cyberattack on August 24, 2024.^[57] Most of the systems were restored by August 31, but the Port of Seattle websites and passenger information systems remained offline.^[58]

Future

The airport has seen record growth in passenger traffic in the 2010s and 2020s. The busiest day for outbound passengers was July 24, 2023, with 73,651 passengers; more than 198,000 passengers (departing, arriving, and connecting) passed through the airport that day. The previous record for outbound passengers was set on August 16, 2019, at 72,154.^[59] The growth has been partly fueled by the nationwide expansion of Seattle-based Alaska Airlines and by Delta Air Lines setting up a major international hub at SEA Airport. That growth has strained the airport's facilities and led the port to invest more than $2 billion into several expansion and renovation projects.^[60]

The airport has six outbound baggage handling systems with limited to no cross-connectivity. The system now in place is aging and reaching its maximum capacity. A $320.4 million project will create one unified, high-speed baggage system under the airport.^[48] That will allow bags to be checked from any ticketing counter, to receive security screening faster, and to be routed to any gate in the airport. The extra efficiency and speed will allow the airport to handle more baggage in the future without expanding the footprint of the baggage handling systems. The initial phase of the project was finished in 2018 and the entire system is scheduled to be completed in 2027.^[50][61]

With estimates that the Puget Sound region will grow by another one million people by 2035, the Port of Seattle began developing the Sustainable Airport Master Plan (SAMP) in 2018 to meet passenger and cargo demands. The SAMP recommends more than 30 projects to improve efficiency and airport access, including a new terminal with 19 gates and an automated people mover through three separate stations.^[62] Near-term projects that are scheduled to be completed in the 2020s include restroom renovations, security checkpoint expansion, and roadway realignment.^[63] A four-story addition to the existing structure of Concourse C began in 2023 and is scheduled to be completed in 2027 at a cost of $399 million; it includes a "central gathering place" under a large wooden ceiling.^[64] Further projects include an automated parking garage guidance system, a gateway project in cooperation with Alaska Airlines, Concourse A building expansion for lounges, improved curbside safety and accessibility, continued refurbishment of the Central Terminal, and a replacement of controls pertaining to the SEA Underground shuttles.^{[citation needed]}

Terminals

The airport has 115 gates^[65] in four concourses and two satellite buildings.^[66] The two satellite terminal buildings, named the North and South Satellites, are connected to the four concourses in the main terminal by a three-line automated people mover system called the SEA Underground. The underground transit system moves passengers within the four concourses of the central terminal and out to the two satellite terminals.^[67]

All non-precleared international arrivals arrive at the South Satellite or Concourse A, regardless of their departure terminal.^[68] A dedicated international arrivals facility with customs control is on the southeast side of the terminal building and connected to the South Satellite via an overhead walkway and to the Concourse A gates via sterile walkways.^[56] The overhead bridge from the South Satellite is 780 feet (240 m) long and rises 87 feet (27 m) over a taxiway.^[56]

• Concourse A contains 16 gates,^[66] and is primarily used by Delta Air Lines, United Airlines, and several international carriers.^[69]
• Concourse B contains 17 gates,^[66] and is primarily used by Delta Air Lines and Southwest Airlines.^[69]
• Concourse C contains 27 gates,^[66] and is used exclusively by Alaska Airlines.^[69]
• Concourse D contains 17 gates,^[66] and is mainly used by Alaska Airlines and American Airlines.^[69]
• North Satellite contains 20 gates,^[66] and is used exclusively by Alaska Airlines.^[69]
• South Satellite contains 14 gates,^[66] and is used by Delta Air Lines, Hawaiian Airlines, and many domestic and international carriers.^[69]

The five security checkpoints at Sea–Tac are located in the main terminal and are managed by the Transportation Security Administration (TSA). All of the checkpoints offer Clear Secure prescreening, while TSA Precheck is available from two.^[70] The airport began using a virtual queuing program, called SEA Spot Saver, in 2021 to reduce wait times and control crowds at security lines.^[71] Wait times at the TSA checkpoints during peak departure periods averaged 20 minutes in 2019 and increased during the COVID-19 pandemic, with a maximum of 90 minutes reached in June 2023.^[72] During particularly busy periods, the queues for security have backed up into the airport's main parking garage and caused several hours of delays for passengers.^[70]

The Port of Seattle maintains and curates a collection of public artwork at Sea–Tac that began with acquisitions in 1968 and was formalized with a percent for art ordinance passed in 2000.^[73] The airport's art collection comprises 289 works, which includes paintings, murals, stained glass pieces, video art, and sculptures, and is valued at $40 million.^[74] A live music program began as a one-year pilot in 2013 with 20 musicians who performed for 780 total hours.^[75] It was expanded into a permanent airport fixture the following year during daytime hours and was temporarily replaced by a video wall during the COVID-19 pandemic in 2021.^[76]

Airfield

The three parallel runways run nearly north–south, west of the passenger terminal, and are 8,500 to 11,900 feet (2,600–3,600 m) long.^[1] In calendar year 2023, the airport had 422,508 aircraft operations, or 1,158 per day: 99% commercial, <1% air taxi, <1% general aviation, and <1% military.^[77]

A new control tower was built beginning in 2001 and opened in November 2004, at the cost of $26 million.^[78] The floor of the new tower's control cab is 233 ft (71 m) above ground level; the tower's overall height including antennas is 269 ft (82 m). The cab has 850 sq ft (79 m²) of space and was designed to support operation by ten controllers, with possible future expansion up to 15. The site and construction method of the tower were designed to maximize the visibility and efficacy of radar systems. The airport's original control tower, built in the 1950s, is now part of the passenger terminal and used as a ramp control tower after being repaired from damage caused by the 2001 Nisqually earthquake.

A recurring problem at the airport is the misidentification of the westernmost taxiway, Taxiway Tango, as a runway. A large "X" has been placed on the north end of the taxiway, but many aircraft have landed on the taxiway.^[79] The FAA issued an alert notice dated from August 27, 2009, to September 24, 2009, urging airplanes about taking precautions such as REILs and other visual cues while landing from the north.

In 2007, the airport became the first to implement an avian radar system providing 24-hour monitoring of wildlife activity across the airfield. This pilot program, designed and implemented with the assistance of the University of Illinois Center of Excellence for Airport Technology (CEAT), was intended to decrease potentially fatal incidents involving collisions with birds and to provide a test bed for the implementation of the technology in the US, which was expected to begin in 2009. The technology is part of a strategy to reduce the presence of wildlife on the airfield.^[80]

Other facilities

The Seattle office of the National Weather Service operates a weather station at the airport, with a temperature gauge between the center and eastern runways. The airport has served as Seattle's official weather recording location since 1945.^[81]

As of April 2023^[update], Sea-Tac has over 23,000 total workers, including 400 to 500 customs agents and 850 TSA security officers. The airport has 3,800 cameras that are monitored from a control center staffed by Port of Seattle Airport Operations personnel. A separate control center monitors the baggage handling system at Sea-Tac, which includes 10 miles (16 km) of conveyor belts and handled 14.5 million pieces in 2022.^[82] Sea-Tac is the first major airport in the U.S. to use filters to remove per- and polyfluoroalkyl substances from its firefighting foam, which had sickened firefighters and workers.^[83]

Passenger

Cargo

This section needs additional citations for verification. (August 2020)

Top destinations

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Busiest domestic routes from SEA (September 2023 – August 2024)^[165]

Rank	City	Passengers	Carriers
1	Anchorage, Alaska	1,017,000	Alaska, Delta
2	Los Angeles, California	1,006,000	Alaska, American, Delta, Spirit, United
3	Las Vegas, Nevada	966,000	Alaska, Delta, Frontier, Southwest, Spirit
4	Phoenix–Sky Harbor, Arizona	956,000	Alaska, American, Delta, Frontier, Southwest
5	Denver, Colorado	953,000	Alaska, Delta, Frontier, Southwest, United
6	San Francisco, California	771,000	Alaska, Delta, United
7	Dallas/Fort Worth, Texas	738,000	Alaska, American, Delta, Frontier
8	Chicago–O'Hare, Illinois	737,000	Alaska, American, Delta, United
9	San Diego, California	613,000	Alaska, Delta
10	Atlanta, Georgia	584,000	Alaska, Delta

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Busiest international routes from SEA (July 2023 – June 2024)^[166]

Rank	City	Passengers	Carriers
1	Vancouver, Canada	646,982	Air Canada, Alaska, Delta
2	London–Heathrow, United Kingdom	563,733	British Airways, Delta, Virgin Atlantic
3	Seoul–Incheon, South Korea	529,639	Asiana Airlines, Delta, Korean Air
–	Tokyo-Haneda and Tokyo-Narita, Japan combined	388,757	All Nippon Airways, Delta, Japan Airlines
4	Paris–Charles de Gaulle, France	292,848	Air France, Air Tahiti Nui, Delta
5	Amsterdam, Netherlands	279,746	Delta
6	Tokyo–Haneda, Japan	276,520	All Nippon Airways, Delta
7	Taipei–Taoyuan, Taiwan	274,479	Delta, EVA Air
8	Frankfurt, Germany	267,026	Condor, Lufthansa
9	Cancún, Mexico	255,829	Alaska, Delta
10	Doha, Qatar	240,416	Qatar Airways

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Airline market share

Annual traffic

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Annual passenger traffic at SEA airport. See Wikidata query.

Annual traffic at SEA

More information Year, Passengers ...

SEA Airport Annual Passenger Data 2011-Present^[167]

Year	Passengers	% Change
2011	32,823,220	—
2012	33,223,111	01.22%
2013	34,826,741	04.83%
2014	37,498,267	07.67%
2015	42,340,537	012.91%
2016	45,737,115	08.02%
2017	46,934,619	02.62%
2018	49,849,520	06.21%
2019	51,829,239	03.97%
2020	20,061,507	061.29%
2021	36,154,015	080.36%
2022	45,964,321	027.13%
2023	50,877,260	010.69%

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