The appearance of the two-seat Su-57D delighted foreigners: India had been waiting for such an aircraft for 16 years
Russia created the tandem version independently, although New Delhi had requested a similar fighter back in the 2010s
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Russian Engines for MiG-31M, MiG 1.42, and Su-57 Fighters Recognized as World's Best in the USA
Two of these fighters never went into serial production