“Mathias Rust is a German aviator known for his illegal landing on May 28, 1987 near Red Square in Moscow. As an amateur pilot, he flew from Finland to Moscow, being tracked several times by Soviet air defence and interceptors… He landed on Vasilevski Spusk next to Red Square near the Kremlin in the capital of the USSR.
Rust’s successful flight through a supposedly impregnable air defense system had a great impact on the Soviet military and led to the firing of many senior officers… The incident aided Mikhail Gorbachev in the implementation of his reforms (by removing numerous military officials opposed to him), and reduced the prestige of the Soviet military among the population, thus helping bring an end to the Cold War.” (Via Wikipedia)