Issued in April 1918 - the very month that the R.A.F. was founded out of the Royal Flying Corps - this booklet is an instructional manual on the use of the American-made Lewis Gun, which was fast becoming the standard British machine gun of the Great War - in the air as well as on the ground.The booklet contains instructions for stripping the gun; notes on its mechanism; its care and cleaning; the likely causes of jams and stoppages; minor repairs; spare parts; ammunition and aiming. This booklet is a facsimile reprint of the copy held in the War Office Library and contains amendments and additions typed and pasted into the original.