I watched this movie at least 200 times on Showtime/The Movie Channel/HBO/Cinemax in 1983/84. THINK IN RUSSIAN.
I didn't know until today that it was loosely based on the 1976 defection of Soviet pilot Viktor Belenko and the "mysterious, advanced MiG-25 Foxbat" which while not better than Western airframes was more advanced than anything the Soviets currently had.