Though the Nie 31 (it had been flown and subsequently abandoned before the company changed its name to Nieuport-Delage) was technically a sesquiplane, it could equally well be described as a shoulder-wing monoplane with a small foreplane.

The lower wing had parallel chord and straight edges, providing a lifting surface with about 40% the area of the main plane.

[2] The Nie 31 was powered by a 130 kW (180 hp) Le Rhone 9R nine-cylinder rotary engine, smoothly and completely cowled.

The fuselage, like that of the earlier Nieuport Nie 29, was a smooth wooden monocoque shell of tulipwood, produced by winding thin spiral strips around a mould in a series of alternately handed layers and glueing them together.

A flight test programme conducted through 1919 showed that the Nie 31 had excellent performance, especially given the low engine power, but Nieuport did not proceed with its development as a fighter,[2] however the Nieuport-Delage Sesquiplan was a direct evolution of this design, but powered with a Hispano-Suiza 8 water-cooled V8 engine, and was built specifically for racing.