Le Prieur had designed the glider in collaboration with Shirou Aibara, a Lieutenant of the Japanese Navy, and Aikitsu Tanakadate, a professor at Tokyo Imperial University.

The first flight took place in December 1909 just to the East of the University of Tokyo at Shinobazu Pond with Le Prieur sitting on the glider's main wing.

The first flight covered 200 m at an altitude of 10 m.[1] During the First World War he invented the plane-mounted Le Prieur rocket launcher for bringing down observation balloons.

This weapon system, which allowed an airplane to fire a single volley of rockets in close succession (the design planned for simultaneous launch, but technical unreliability made it impossible in 1916) was remarkably effective against the German observation balloons, and was only phased out when tracer rounds and incendiary bullets for the on-board machine guns (with similar efficiency and larger ammunition capacity) became widespread among the Allied air forces near the very end of the war.

The diver's nose was pinched by a pair of spring clamps ("pince nez") to prevent ingress of water, and his eyes were protected by small goggles with rubber surrounds.

Le Prieur was impressed by the simplicity of the Fernez equipment and the freedom it allowed the diver, and he immediately conceived an idea to make it free of the tube to the surface pump by using Michelin cylinders as the air supply.

[3] In 1934 Le Prieur was granted French patent 768083 for an improved hand-controlled self-contained underwater breathing apparatus with full face mask.