First test flight of SPAD S.XIII, a French biplane. Within months, it entered service with Aéronautique Militaire. Used later by Americans.

4 Apr 1917, the first test flight of SPAD S.XIII, a French biplane. Within months, it entered service with Aéronautique Militaire. Used later by Americans. Among the most successful WW1 fighters. Noted for its robust construction & ability to dive at high speed. 8,472 built by end of the war.