Zurich Airport () is the largest international airport of Switzerland and the principal hub of Swiss International Air Lines. It serves Zürich, Switzerland's largest city, and, with its surface transport links, much of the rest of the country. The airport is located north of central Zürich, in the municipalities of Kloten, Rümlang, Oberglatt, Winkel, and Opfikon, all of which are within the canton of Zürich. History Early years In the Zürich area, mixed civil and military air traffic developed from 1909 onwards at Dübendorf airfield, northeast of the city. From 1919, the airport was home to Swissair's predecessor Ad Astra Aero, and from 1932 also to Swissair. The first international flight from Switzerland landed on July 21, 1921. In the early years of aviation, the Dübendorf Air Base, located some to the Zurich Airport, also served as the city's commercial airfield. The need for a dedicated commercial facility led to the search for a location at which to build a replacement airport. In 1939, civil air traffic had to be suspended at the outbreak of the Second World War for military strategic reasons. Although Swissair was allowed to resume scheduled air traffic in September 1940, this remained on a modest scale during the war. In March 1943, the government of the canton of Zürich commissioned a study to identify possible locations for the construction of a major airport. In its report, a consortium of engineers and architects led by Locher & Cie company advised against the previously discussed expansion options at Dübendorf airport and instead recommended a separate civil airport in the partially forested moorland area of the armory situated between Kloten and Oberglatt. In August 1943, the Federal Military Department declared its agreement to abandon the armory as a matter of principal "in the higher national interest". Locher & Cie submitted "Project I" to the Government on 31 December 1943. Four runways were planned and together with the buildings the required area was 472 hectares. Without the purchase of land, the project would have cost 87 million CHF. The government found the costs too high and ordered a revision. The "Project II" of 29 April 1944 still provided for an area of 290 hectares and costs of 65 million CHF, but the government council demanded a further reduction. For "Project III" of 31 July 1944, 54.4 million and 215 hectares were required. The project nevertheless met the requirements of