No. 121 Squadron RAF

No. 121 Squadron was a Royal Air Force (RAF) aircraft squadron that during the Second World War was one of the three Eagle Squadrons manned by American volunteers.

In World War I
No. 121 Squadron Royal Flying Corps (Royal Air Force from 1 April 1918) was formed at Narborough on 1 January 1918 as a day bomber squadron to operate the Airco DH.9. The squadron was equipped with Airco DH.4s for training, but due to delays with the DH.9 and the end of the war approaching, the squadron was disbanded on 17 August 1918 without becoming operational.

In World War II
The squadron was reformed on 14 May 1941 as No. 121 (Eagle) Squadron at RAF Kirton-in-Lindsey, the second of three Eagle Squadrons manned by American volunteers. Equipped with the Hawker Hurricane, the squadron then converted to the Supermarine Spitfire and moved south to RAF North Weald to begin operations on channel sweeps and Rhubarb operations. On 15 November 1941 the squadron claimed its first enemy aircraft destroyed. The squadron then upgraded to cannon-armed Spitfire VBs and carried out offensive operations over the channel and providing bomber escorts.

To the USAAF
In September 1942, the squadron moved to RAF Debden to be with the other Eagle squadrons. The squadron was transferred to the United States Army Air Forces as the 335th Fighter Squadron and officially disbanded as a RAF unit on 29 September 1942. The new squadron became part of the 4th Fighter Group of the Eighth Air Force.