In Japan during the late 1930s and early 1940s, in common with most large economies of the time, research was being conducted into pressurised cabins for high-altitude flight. In similar fashion to the Lockheed XC-35, in the United States, Tachikawa incorporated a pressurised cabin into new forward and centre fuselage sections for one of the locally built Lockheed Type LO Transport Aircraft. The resulting research aircraft was given the long designation Tachikawa-Lockheed Type-B high altitude research aircraft and the company designation Tachikawa SS-1. The first conversion was completed in May 1943, re-engined with 2x Mitsubishi Ha-102 14-cylinder radial engines. The two conversions carried out a brief flight testing programme.