The Norwegian army started using Gardermoen as a camp in 1740, although it was called Fredericksfeldt until 1788. It was first used by the cavalry, then by the dragoons and in 1789 by the riding marines. The base was also taken into use by the infantry from 1834 and by the artillery from 1860. Tents were solely used until 1860, when the first barracks and stalls were taken into use. Insulated buildings were built around 1900, allowing the camp to be used year-round. By 1925, the base had eleven camps and groups of buildings. The first flight at Gardermoen happened in 1912, and Gardermoen became a station for military flights. During the occupation of Norway by Nazi Germany, the Luftwaffe took over Gardermoen, and built the first proper airport facilities with hangars and two crossing runways, both 2,000 metres (6,600 ft) long. After World War II, the airport was taken over by the Norwegian Air Force and made the main air station. Three fighter and one transport squadron were stationed at Gardermoen. Braathens SAFE established their technical base at the airport in 1946, but left two years later. Gardermoen also became the reserve airport for Oslo Airport, Fornebu, when the latter was closed due to fog. From 1946 to 1952, when a longer runway was built at Fornebu, all intercontinental traffic was moved to Gardermoen. Gardermoen grew up as a training field for the commercial airlines and as local airport for general aviation. Some commercial traffic returned again in 1960, when SAS received its first Sud Aviation Caravelle jet aircraft, that could not use the runway at Fornebu until it was extended again in 1962. SAS introduced a direct flight to New York in 1962, but it was quickly terminated. In 1972, capacity restraints forced the authorities to move all charter traffic from Fornebu to Gardermoen. However, SAS and Braathens SAFE were allowed to keep their charter services from Fornebu, so they would not have to operate from two bases. A former hangar was converted to a terminal building and in 1974 passenger numbers were at 269,000 per year. In 1978, SAS started a weekly flight to New York. In 1983, further restrictions were enforced, and also SAS and Braathens SAFE had to move their charter operations to Gardermoen, increasing passenger numbers that year to 750,000. Several expansions of runway were made after the war, and by the 1985-extension the north–south runway was 3,050 metres (10,010 ft). The first airports to serve Oslo were Kjeller Airport which opened in 1912 and Gressholmen Airport which served seaplanes after its opening in 1926. Norway's first airline, Det Norske Luftfartrederi, was founded in 1918 and the first scheduled flights were operated by Deutsche Luft Hansa to Germany with the opening of Gressholmen. In 1939, a new combined sea and land airport opened at Fornebu. It was gradually expanded, with a runway capable of jet aircraft opening in 1962 and a new terminal building in 1964. But due to its location on a peninsula about 8 kilometres (5.0 mi) from the city center and close to large residential areas, it would not be possible to expand the airport sufficiently to meet all foreseeable demands in the future. Following the 1972 decision to move charter traffic to Gardermoen, politicians were forced to choose between a "divided solution" that planners stated would eventually force all international traffic to move to Gardermoen, or to build a new airport. Gardermoen had been proposed as the main airport for Oslo and Eastern Norway as early as 1946, both by the local newspaper Romerikes Blad and by Ludvig G. Braathen, who had just founded Braathens SAFE. In 1970, a government report recommended that a new main airport be built at Hobøl, but stated that the time was still not right. The areas were therefore reserved. During the 1970s, it became a political priority by the socialist and center parties to reduce state investments in Eastern Norway to stimulate growth in rural areas.