World War 1 began with the airplane as a frail, unarmed means of observing enemy troop movements and ended with the airplane as a powerful, much more evolved weapon of war. There were specialized roles for fighter, bomber and ground attack aircraft as well as newly developed aerial strategies and tactics for operational effectiveness.Many aircraft design technologies greatly matured during the war. Four will be the subject of this paper: Drag reduction, aircraft handling qualities, stability and control, airfoil design technology, and structures design technology. Propulsion and armament also matured greatly but are not discussed in the paper.The discussion of drag reduction will illustrate the innovations of the British on external wire bracing drag, the French on cowl design and the Germans on cantilevered wings and induced drag. Control surfaces and handling will show the invention of balanced controls, and the use of the equations of motion to design specific handling properties, as illustrated in several aircraft. Wind tunnel data of the Fokker Eindecker will be shown. Airfoil technology will discuss the innovations utilized by the Germans, which resulted in thick airfoils, allowing for internal, cantilevered structures. Finally, the welding techniques of Fokker's technicians to the all-metal aircraft of Hugo Junkers, will be used to illustrate the advancement of metal construction.