B-29 (USA) ✈ TU-4 (USSR)

Boeing B-29 Superfortress (USA). First flight: 21 September, 1942 (Wiki

Tupolev Tu-4 (USSR). First flight: May 19, 1947 (Wiki)

Stalin told Tupolev to clone the Superfortress in as short a time as possible. The reverse-engineering effort involved 900 factories and research institutes, who finished the design work during the first year; 105,000 drawings were made. By the end of the second year, the Soviet industry was to produce 20 copies of the aircraft ready for State acceptance trials.
— Wikipedia