Silhouettes of military aircraft painted on the ceiling at an RAF training school during the Second World War, 1941. Aircraft identification training enabled personnel to recognise the different types of British and foreign planes: 'silhouettes are numbered and provide not only useful training but also useful practice for those who find memorising the characteristics of the different types difficult.' From "The Royal Air Force in Pictures", 2nd edition, by World War I flying ace Major Oliver Stewart. [Country Life Ltd, London, 1941]