Many straight engines have been produced for aircraft, particularly from the early years of aviation and through the interwar period leading up to the Second World War.
Prominent examples include the German Mercedes D.III and BMW IIIa, Italian Isotta Fraschini V.4 and British Siddeley Puma.
The British de Havilland Gipsy family of engines and their descendants included straight-four and straight-six upright and inverted air-cooled engines which were used on a wide range of smaller aircraft around the world, including on the Tiger Moth biplane, and helped made the configuration popular for light aircraft.
Menasco and Fairchild-Ranger in the United States, Renault in France, Walter in Czechoslovakia, and Hirth in Germany all built a similar range of engines which were popular in their respective markets.
Since the thrust line is higher, the engine can be mounted lower in the airframe, improving visibility forward, which is no longer blocked by the cylinder heads.