In September, 1942, the RAF Eagle Squadrons were transferred to the United States Army Air Force.
America had joined the war in December, 1941, and had begun to send forces to Britain in mid-1942. There was pressure to transfer the experienced pilots of the Eagle Squadrons to the American forces, but there were several problems. Many of the pilots had failed the USAAF medical tests before they had volunteered for the RAF. None had ever been awarded US pilot's wings either.
The USAAF wanted to split the squadrons up, to spread their experience around, while the pilots wanted to stay in their own squadrons. There were also insufficient aircraft available, until the USAAF acquired Supermarine Spitfires. Finally, many of the pilots were reluctant to leave their adopted force to join the more formal USAAF, despite the guaranteed commissions for the sergeant pilots, promotions for the officers, and higher rates of pay.
Nevertheless, on 29 September, 1942, the Eagle Squadrons joined the 4th Pursuit Group, VIII Fighter Command.
Nos.71, 121 and 133 Squadrons, RAF, became 334th, 335th and 336th Squadrons respectively.
Above is archive footage of the ceremony of the RAF's Eagle Squadrons transfer to the command of the Eighth Fighter Command, USAAF Eighth Air Force. Several senior RAF and USAAF dignatories are in attendance, along with members of the press.
Image: IWM FRE 2333
Pilots of the Eagle Squadron in their new American Army Air Corps uniforms, besides their Spitfires, seen with the new American markings at their operational station in England. AND. Sept. 1942.
Note that the aircraft retained their "XR" squadron codes, which would change in 1943 when they were re-equipped with P-47 Thunderbolts.