Itami Airport opened as No. 2 Osaka Airport (第二大阪飛行場, Dai-ni Ōsaka Hikōjō) in 1939. Prior to the opening of Itami, Kizugawa Airport was Osaka's main civilian airport. It handled both seaplanes and conventional ones. The site of Kizugawa Airport is now a port area in Funamachi in south end of Taisho Ward with only a small marker located in Funamachi Ryokuchi Park below the Shin-Kizugawa Bridge.

In 1931, the Osaka municipal government drafted plans to construct a new "No. 1 Osaka Airport" near the mouth of the Yamato River, also targeted at seaplanes, but concerns about fog and protests from Kobe-based businesses led the government to build the "No. 2 Airport" for land-based aircraft instead.

Construction began in July 1936 on a 53-hectare (131 acre) site. The new airport opened on January 17, 1939, and was primarily used by the Imperial Japanese Army during its early years. It had four runways at the time, ranging in length from 1,100 to 1,600 m, and could handle aircraft as large as the Douglas DC-3.

U.S. occupation

U.S. occupation forces took over Osaka No. 2 Airport after the end of World War II in 1945, expanding it to 221 hectares and renaming it Itami Air Base. The airfield was used extensively by US forces during the Korean War. In 1954, Marilyn Monroe and Joe DiMaggio stopped at Itami during their honeymoon, and in 1956, the base was used in the filming of the movie Sayonara.

Japan Airlines operated its inaugural flight between Itami and Tokyo's Haneda Airport on October 25, 1951, using a Martin 2-0-2 aircraft leased from Northwest Airlines. JAL initially operated from a small joint-use section of the U.S. air base.

Itami was fully returned to the Japanese government in March 1958, and was renamed Osaka Airport (大阪空港, Ōsaka Kūkō) in March 1958 and Osaka International Airport in July 1959.

International era (1950s-1994)

Japan Airlines and Cathay Pacific opened international flights from Osaka to Hong Kong in 1960. Although Itami saw its first passenger jet service (Caravelle service from Thai Airways International) in 1964, the runways and terminals at Osaka lacked the capacity to handle larger jets such as the de Havilland Comet, Douglas DC-8 and Boeing 707, which had already begun operating at Tokyo's Haneda Airport in 1959.

The Japanese government quickly implemented a plan to expand Osaka Airport by an additional 82.5 ha so that it could accommodate jet aircraft. Despite some protests from locals, the plan was approved by the neighboring city assemblies between 1960 and 1961 with strong backing from local business groups, and land was purchased between 1962 and 1964, in part out of the aviation industry's interest in keeping pace with the development of the Tokaido Shinkansen high-speed rail link between Tokyo and Osaka. The current main runway was completed in 1970.

In its heyday Itami was served by a variety of major international carriers, including Pan Am (Japan routes transferred to United in 1985), British Airways, Air India, Cathay Pacific and Korean Air.

Northwest Airlines was a major international operator at Itami, and by 1992 offered nonstop service to New York, Los Angeles, Honolulu and Sydney. The Sydney service became the focus of a rare aviation agreement dispute between the United States and Australia, as less than 30% of passengers on the Australia-Japan segment were originating in the U.S. even though the "primary objective" of the route authority, according to the US-Australia aviation agreement, was service between the US and Australia. In 1993, after Australia demanded arbitration and the US implemented retaliatory sanctions against Qantas, Northwest was forced to limit the amount of local Australia-Japan traffic on the Osaka-Sydney route, and subsequently abandoned the service entirely.

BOAC operated in Osaka until 1974, flying from either Taipei or Tokyo.

Political friction

While Japan's economy was growing rapidly, the area around Itami Airport became an increasingly dense residential area for commuters to Osaka.

A number of factors made the airport an intensely debated political issue in the 1960s and 1970s, among them:

The introduction of jet aircraft made noise and air pollution a growing concern among locals.

The United States Armed Forces had rights to use Itami Airport for refueling and maintenance, and frequently sent military aircraft there for overhauls at the Shin Maywa Industries plant there. This activity caused consternation among locals who were opposed to the Vietnam War.

Jet flights at Itami began on June 1, 1964, and triggered complaints by neighboring residents about noise pollution. In addition, eminent domain procedures were used in 1966 to obtain land for the runway expansion at Itami and led to local protests, as had also been the case in the construction of Narita International Airport near Tokyo.

In May 1968, a group of local citizens decided to sue the government for damages related to noise pollution from Itami Airport. The lawsuit was filed in December 1969. The Japanese government concurrently banned takeoffs and landings at Itami between 10:30 PM and 6:30 AM, effective February 1970.