No. 21 Squadron

No. 21 Operational Training Unit was established on 21 January 1941 at RAF Moreton-in-Marsh in Gloucestershire, formed from a cadre drawn from No. 15 OTU, to prepare night bomber crews on the Vickers Wellington. The airfield was still under construction at the time and the first course did not begin until 1 March, initially with only two aircraft; further courses followed at roughly fortnightly intervals as the unit expanded. Originally placed within No. 6 Group, the unit transferred to No. 91 Group on 11 May 1942, reflecting the growing organisational distinction between operational and training formations within Bomber Command. In the summer of 1942 the unit contributed aircraft to the Thousand Bomber raids, emerging from the first of those operations without loss. Satellite airfields at Edgehill and later Enstone supplemented the main station and allowed the volume of flying to grow as demand for trained crews intensified. Wellington variants from the Ic through to the Mark X remained the unit’s standard type throughout the war, with aircrew losses to accidents and enemy action numbering over 120 during the course of the unit’s service. After the war the unit relocated to RAF Finningley in November 1946 and was redesignated No. 202 Advanced Flying School in March 1947.