I'll give you another example
The Grumman X-29 was a USAF FSW aircraft that was co-developed by Sukhoi and Grumman in the mid to late 1980's. The SU-37 Russian derivative was a similar concept that arrived after the X-29
The concepts and technologies the fighter-size X-29 explored were the use of advanced composites in aircraft construction; variable camber wing surfaces; the unique forward-swept-wing and its thin supercritical airfoil; strake flaps; and a computerized fly-by-wire flight control system that overcomes the aircraft's instability. They were flight tested at Dryden from 1984 to 1992 in a joint NASA, DARPA (Defense Advanced Research Projects Agency) and U.S. Air Force Program, and made a total of 374 combined flights.
So, fundamentally the forward swept wing allows a high degree of manouvrability but requires extremely thin wings. The US abandoned it and the joint venture with Sukhoi as they did not see any benefit in investing high compound polymers etc into its development (as conformal polymer products etc were quite expensive). About 10 years later the russians decided to run with the project on their own as the cost of materials had come down enough to make it more practical.
Both planes were concept demonstraters and were not seen as viable for full production as frontline fighters, but both provided substantial information for other aircraft that both countries were developing.
The X-29 has its heritage in the F-5 and F20 series fighter family and the Berkat has its heritage linked to the SU-27 concept.
