On May 28, 1987, the 19-year-old pilot from West Germany, Matthias Rust, entered the airspace of the USSR in a small "Cesna" plane without hindrance and landed on Red Square in Moscow. He was immediately detained and was not released until August 3, 1988.
He told the arriving KGB officers that he wanted to speak with Soviet leader Mikhail Gorbachev.

As crazy as this story may seem, the circumstances surrounding the events of May 28, 1987 are much more incredible:
On this day, the Soviet Union celebrates Border Guard Day.
And on the very day of the professional holiday of those who have to guard the state border, a 19-year-old German youth makes fun of the entire Soviet air defense (ADF).
However, experts recall that in the late 1980s it was fashionable among Soviet collective farm chairmen to have small planes. They were used for tourist tours with the dignitaries who arrived from the Kremlin.
The map shows that during part of the flight it was taken for a training plane.
Rust himself takes a short break before flying to Moscow.
Mikhail Gorbachev is so angry that he declares: "If a plane can fly over Soviet territory undisturbed and not be noticed at all, this shows how poorly our air defense works". Shortly thereafter, the Minister of War, the Chief of the Air Force, and 300 other officers were immediately dismissed.
In practice, two fighter jets were raised on alert and after intercepting the “Chesna“ Matthias Rust was released from prison 18 months later after the then German Foreign Minister Hans-Dietrich Genscher personally intervened on his behalf. Muscovites began to joke about the incident and began to call Red Square Sheremetyevo No. 3 (Sheremetyevo 1 and 2 are airports near Moscow).