Low Flying Avoid Barrages. A Royal Air Force technical diagram O.T.5 1750 dated 21.10.18 depicting low flying aircraft and shells bursting with the legends 'British machine returning from a low ground patrol unnecessarily returning through barrage thereby running a great risk of being hit' and 'British machine returning from a low ground patrol with comparative safety by avoiding barrage' and 'Don't fly through our own or the enemy's barrage unless absolutely necessary even though it may necessitate flying low for a longer time over hostile country'. Framed and glazed - 18 x 25¼ins. (45.7 x 64.2cm.)