Ukrovozdukhput / Ukranian Air Transport Co

This company (The Ukranian Air Transport Co) was one of the most important aviation companies in Russia in the 1920s. Besides operating several airlines, Ukrovozdukhput manufactured aircraft to the designs of K. A. Kalinin, who patented the elliptical wing planform in 1923. One of his best-known designs was the 1928 Kalinin K-4 single engined cabin monoplane, produced as a transport or air ambulance.