The B-29 glider was good enough to copy for decades:
https://en.wikipedia.org/wiki/Tupolev_Tu-4
The Tupolev Tu-4 (Russian:Туполев Ту-4; NATO reporting name: Bull) is a piston-engined Soviet strategic bomber that served the Soviet Air Force from the late 1940s to mid-1960s. The aircraft was a reverse-engineered copy of the American Boeing B-29 Superfortress.