Osaka International Airport (伊丹空港 Itami Kūkō) (IATA: ITM, ICAO: RJOO), often referred to as Itami Airport (大阪国際空港 Ōsaka Kokusai Kūkō) is the primary regional airport for the Kansai region of Japan, including the major cities of Osaka, Kyoto and Kobe. Construction began in July 1936 on site. The airport was primarily used by the Imperial Japanese Army during its early years. U.S. occupation forces took over Osaka Airport after the end of World War II in 1945, and renaming it Itami Air Base. The airfield was used extensively by US forces during the Korean War. Itami was renamed Osaka Airport (大阪空港 Ōsaka Kūkō) following its return to Japanese control in March 1959. Despite its "international" designation, the airport's scheduled passenger air traffic is entirely domestic and Japan's 3rd busiest airport.