The Curtiss OX-5 engine is the first mass-produced U.S. designed aircraft engine. Introduced in 1915, the OX-5 was a liquid-cooled V-8 engine, which powered the famous Curtiss JN-4 “Jenny.” In 1929, 38% of all licensed aircraft in the United States utilized the OX-5. To this day, many OX-5 engines are still in use and favored by vintage aircraft pilots and restorers.