Fuji Heavy Industries is continuing to develop a fixed-wing unmanned air vehicle that can be deployed from under the wing of a fighter aircraft.
The conglomerate is developing the UAV for Japan's air force, say industry sources in the country. It has built two so far, but lost one during testing, they add.
The UAV was deployed from under the wing of an air force Mitsubishi/Lockheed Martin F-2 fighter before plunging into the sea, and was not recovered, the sources say.
Officials at Fuji have declined to comment.
Fuji is the smallest of Japan's three major aerospace conglomerates. Mitsubishi has the lion's share of fighter manufacturing, while Kawasaki Heavy Industries is dominant in military transports.
In recent years Fuji has tried to grow its business by investing in the development of UAVs for military and commercial customers.
It built three forward flying observation system unmanned helicopters for the Japanese army's artillery units. It also developed a civil version of the design dubbed the RPH-2, which carries a chemical pesticide tank and spray boom for agricultural use.