 Air Vietnam also used the facility from 1951 to 1975 for civilian domestic and international flights within Southeast Asia.On 22 September 1940, the Vichy Government signed an agreement with Japan allowing the Japanese to station troops in Tonkin and use three airfields there.On 14 July 1941, the Japanese sent the French an ultimatum demanding the use of bases in Annam and Cochinchina, the French acquiesced and by late July, the Japanese occupied Cam Ranh Bay, Bien Hoa Air Base and Tourane Airfield.