During WW2 a few B29s had to make emergency landings in Russia. Stalin decided to steal the design. He ordered that bolt-for-bolt exact duplicates be built, as a way to inject new technology into their aviation programs. And to intimidate the west, these new planes were shown to the world during the 1947 Aviation Day parade. The Russians went on to build 850 of them. http://rb-29.net/html/03relatedstories/03.03shortstories/03.03.10contss.htm
I wonder how many Russian copies still fly. The last I heard a few years ago, we were down to 2 flying B-29's. There were some others looking for parts to get some more airworthy.
I once read that the Chinese had so completely copied the DC-3/C-47 airplane that virtually all parts were interchangeable. (Side note: knockoff Chinese parts are responsible for why so many DC-3's still fly.) I wouldn't fly in a DC-3 that had a Chinese gas cap. (I used to import goods from the Far East and I am aware of certain quality control issues from certain countries.)