Early years

In the Zurich 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 regular international flight service began on 1 June 1922 with an Ad Astra route to Fürth, Germany. In the early years of aviation, the Dübendorf Air Base, located around 9 km (5.6 mi) southeast of Zurich Airport, also served as the city's commercial airfield. The need for a dedicated commercial facility led to the search for a location 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 conflict.

In March 1943, the government of the canton of Zurich commissioned a study to identify possible locations to construct a major airport. In its report, a consortium of engineers and architects led by Locher & Cie advised against the previously discussed expansion options at Dübendorf and instead recommended a separate civil airport in the partially forested moorland area of the armoury situated between Kloten and Oberglatt. In August 1943, the Federal Military Department declared its agreement to abandon the armoury as a matter of principle "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 (1,170 acres). Without the purchase of land, the project would have cost CHF 87 million. 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 (720 acres) at a cost of CHF 65 million, but the government council demanded a further reduction. For "Project III" of 31 July 1944, CHF 54.4 million and 215 hectares (530 acres) were required. The project nevertheless met the requirements of an intercontinental airport. The Government formally approved it and submitted it to the Federal Government, strongly emphasising that the Zurich project was "far superior" to the also planned (and ultimately abandoned) Swiss Central Airport Utzenstorf, near Bern.

In December 1944, the responsible Federal Councillor, Enrico Celio, explicitly spoke out in favour of Zurich-Kloten, in a letter to his counterparts, as did the governments of the cantons of Eastern and Central Switzerland and Ticino a month later. The National Council and Council of States followed this view and on 22 June 1945 approved the "Federal Decree on the Expansion of Civil Airports". Basel, Bern and Geneva were to receive smaller continental airports and be supported with a 30 percent share of the costs. The Zurich project was granted the status of an intercontinental airport and the highest possible subsidy rate of 35 percent.

Switzerland's federal parliament decided in 1945 that Zurich was to be the site of a major airport, and sold 655 hectares (1,620 acres) of the Kloten-Bülach Artillery Garrison (German: Artillerie-Waffenplatz Kloten-Bülach) to the canton of Zurich, giving the canton control of the new airfield. Construction of the airport began the following year.

Initial plans for the airport, as laid out in the Federal Government's scheme of 1945, were centred on facilities capable of handling international airline traffic. Aircraft of up to 80 tonnes were envisaged. The primary runway was to be designed for use in all weather conditions and at night, with a 400-metre (1,300 ft)-wide hard surface running to 3,000 metres (9,800 ft) in length. Additional 100-metre (330 ft) areas were to be provided on the shoulders for lateral protection in case of runway excursions. Additional domestic runways, between 1,000 and 1,400 metres (3,281 and 4,593 ft) in length, were also to be built.

First stage of construction: civil engineering

On 25 February 1946, the Cantonal Council of Zurich approved a building loan of CHF 36.8 million. The cantonal referendum of 5 May 1946 resulted in a clear approval with 105,705 votes in favour and 29,372 against. "Project IV" never came to fruition, as it was further developed by adapting it to the ICAO standards which were changing rapidly at the time. Instead of four runways, the new "Project V" of 20 May 1946 provided only three. Project VI" of 9 October 1946 increased the dimensions of all three runways. Finally, the slightly modified "Project VII" of 20 December 1947 was realised. Within three years, the design on the drawing board had completely changed from a purely grass airfield with a four-runway system without taxiways to a three-runway system with paved taxiways. The staggered design meant that it was possible to react to changes without having to impose a complete halt to construction.

Construction works finally began on 5 May 1946 with the diversion of the Altbach stream.