The 334th was constituted on 22 August 1942 as an incorporation of the No. 71 Squadron RAF, an Eagle Squadron of American volunteers in Great Britain's Royal Air Force (RAF). After the United States entered the war, the squadron was transferred to the U.S. Army Air Forces (USAAF). It was officially constituted by War Department letter on 12 August 1942, and was activated at Bushey Hall, England on 12 September 1942.