[3][4] The base was built during World War II by the United States Army as part of its mission to maintain the defense of Iceland and secure northern Atlantic air routes.

In 2017, the United States announced its intention to modify the largest hangar on the Icelandic base in order to house the new Boeing P-8 Poseidon ASW aircraft being introduced.

In 1939, with war imminent in Europe, the German Reich pressed for landing rights for Deutsche Luft Hansa's aircraft for alleged trans-Atlantic flights.

[citation needed] A British request to establish bases in Iceland for the protection of the vital North Atlantic supply lines after German forces occupied Denmark and Norway in April 1940 was also turned down in accordance with the neutrality policy.

In addition to their defense role, U.S. forces constructed the Keflavik Airport as a refueling point for aircraft deliveries and cargo flights to Europe[citation needed].

The airport was built by the United States military during World War II, as a replacement for a small British landing strip at Garður to the north.

[6] With the end of the war in Europe, Keflavik Airport became a transit point for aircraft returning from the European Theater of Operations to the United States.

In 1949, Iceland voted to join the North Atlantic Treaty Organization (NATO) among protests about the US militarizing the country, and the base assumed the status of significant strategic importance in the Cold War.

During 1947–51, while the base was operated by a U.S. civilian contractor company most of the World War II temporary structures were left empty and became badly deteriorated.

The contractor had extended one runway, constructed a new passenger terminal and hotel building, one aircraft hangar, a hospital, housing units and other facilities for the staff.

ADC, later renamed Aerospace Defense Command used the facility for air surveillance of Iceland and the North Atlantic, employing F-102 Delta Dagger and then F-4C Phantom II fighters as interceptors.

[citation needed] In 1974, the left-wing Government of Iceland's new proposal to close the base triggered a petition that garnered 55,000 signatures, about a quarter of the population of the entire nation.

[8] On 1 October 1979 Tactical Air Command (TAC) absorbed ADC's assets, and the F-4E Phantom II aircraft of the 57th Fighter Interceptor Squadron (57 FIS).

United States Air Forces in Europe (USAFE) took over ACC responsibilities at Keflavik on 1 October 2002 as part of a larger restructuring of the unified commands.

During a six-month transition to reduce the military presence in Iceland, most facilities closed and most of the service members departed, leaving behind a core team of active duty and Reserve personnel to finish the job.

[13] In September 2015, news media reported U.S. government officials expressed a desire to reopen aspects of the NATO base of Keflavik Naval Air Station, to cope with increasing Russian military activity around Iceland.

[14][15] In 2016 the United States began preparations to establish regular patrol rotations at the base,[16] and in 2017 announced its intention to build new hangars to house Navy P-8 Poseidon aircraft.

** Rotational TDY flights of aircraft from 48th Operations Group, RAF Lakenheath, United Kingdom Naval Air Station Keflavik was the host command for all U.S. defense activities in Iceland.

Army National Guard units and Interim Marine Security Forces stormed the lava fields surrounding the base during training exercises such as Northern Viking.

NAS Keflavik employed approximately 900 Icelandic civilians who worked with military personnel, providing the services necessary to operate the base.

In addition, during this same time period, the former Soviet Union constructed one of their largest embassy facilities in the nearby capital, Reykjavik, which doubled as a diplomatic cover for intelligence collection activities against U.S. and NATO military forces.

The base offered a wide variety of recreational services which included bowling, swimming, gymnasium, theater, social clubs, a Wendy's restaurant, and hobby centers.

Other services included a Navy Exchange, commissary, bank, credit union, hospital, beauty shop, tour office and morale flights to the rest of Europe and the United States.

NAS Keflavik also features prominently in Icelandic author Arnaldur Indriðason's 1999 mystery thriller Napóleonsskjölin, published in English in 2011 as Operation Napoleon.