This article explores the British Commonwealth Air Training Plan (BCATP), the RAF's major scheme for training airmen during the Second World War. Through this training programme, the dominions of Canada, Australia and New Zealand provided an indispensable contribution to the generation of British air power, a necessary condition for eventual victory. The article first considers the precise ways in which the BCATP extended British air strength, through an analysis of the output of graduates in the UK and the dominions. This is followed by an examination of how the governments of Australia and Canada attempted to ensure the continued national identification of their personnel once these airmen were serving within the RAF, reflecting the increasing political independent-mindedness of the dominions. Although Canada pursued a bolder and more successful policy of ‘Canadianization’, the mixed reception that this initiative received from airmen demonstrated the fact that the importance of national identification to Canadian airmen in Europe varied widely depending on individual experiences; indeed, national political currents were moving ahead of any broad consensus among servicemen.