The position to which aircraft construction has proceeded is due in a large measure to the intense metallurgical investigations of recent years. Amongst the materials that have arisen out of this are the light alloys of aluminium, and in particular, that known by the general name “duralumin.” This alloy plays the part of main structural material in many of our present-day aircraft. The object of this paper is to give a brief general account of duralumin with reference to aircraft construction.