Guilty of Hooliganism!

"Mathias Rust (born 1968) is a German pilot who, in 1987, at the age of 19, flew from Hamburg to Moscow, eluding the Soviet air defences and landed in Red Square near the Kremlin.

After leaving Hamburg on May 28 Rust refuelled his Cessna 172B at Helsinki-Malmi Airport. He told air traffic control that he was going to Stockholm, but he turned his plane towards the east. Rust disappeared from the Finnish air space near Sipoo. He headed towards the Baltic coastline and turned towards Moscow. By chance, he flew into the Soviet Union on the national border guard's holiday, and the lax security that resulted allowed him to fly into Soviet territory unnoticed. Rust flew straight towards Moscow and landed in Red Square. He was arrested immediately by the Soviet authorities.

Mikhail Gorbachev took advantage of this, replacing the defense and air defense ministers (both of whom were opposed to glasnost and perestroika) with men who supported his policies. More than 2,000 officers (again, most of whom were opposed to Gorbachev's reform) lost their jobs. This move was critical in winning over the previously fiercely conservative and anti-reform military.

Rust's trial started in Moscow on September 2, 1987. He was sentenced to four years in a labour camp for hooliganism, disregard of aviation laws and infringement of the Soviet border. After a prison sentence of 432 days in the Soviet Union, he was returned to West Germany on August 3, 1988, after serving 18 months in a Soviet prison."

-from Wikipedia.