Parasol wing

A monoplane is a fixed-wing aircraft with a single main wing plane, in contrast to a biplane or other multiplane, each of which has multiple planes.

A monoplane has inherently the highest efficiency and lowest drag of any wing configuration and is the simplest to build. However, during the early years of flight, these advantages were offset by its greater weight and lower manoeuvrability, making it relatively rare until the 1930s. Since then, the monoplane has been the most common form for a fixed-wing aircraft.

Although the first successful aircraft were biplanes, the first attempts at heavier-than-air flying machines were monoplanes, and many pioneers continued to develop monoplane designs. For example, the first aeroplane to be put into production was the 1907 Santos-Dumont Demoiselle, while the Blériot XI flew across the English Channel in 1909. Throughout 1909–1910, Hubert Latham set multiple altitude records in his Antoinette IV monoplane, eventually reaching 1,384 m (4,541 ft).

The equivalent German language term is Eindecker, as in the mid-wing Fokker Eindecker fighter of 1915 which for a time dominated the skies in what became known as the "Fokker scourge". The German military Idflieg aircraft designation system prior to 1918 prefixed monoplane type designations with an E, until the approval of the Fokker D.VIII fighter from its former "E.V" designation. However, the success of the Fokker was short-lived, and World War I was dominated by biplanes. Towards the end of the war, the parasol monoplane became popular and successful designs were produced into the 1920s.

Nonetheless, relatively few monoplane types were built between 1914 and the late 1920s, compared with the number of biplanes. The reasons for this were primarily practical. With the low engine powers and airspeeds available, the wings of a monoplane needed to be large in order to create enough lift while a biplane could have two smaller wings and so be made smaller and lighter.

...
Wikipedia