MOSCOW — Mathias Rust, the 20-year-old West German pilot who amazed the world by landing his small plane in Red Square last year, was freed Wednesday after serving a year of a four-year sentence in a Soviet prison.
Rust, who buzzed the Kremlin in his single-engine Cessna before landing in Red Square in May, 1987, on what he said was a peace mission, was granted clemency by the Supreme Soviet, the country's Parliament, and put on an airliner to Frankfurt.
"I will continue the work for peace," he told reporters while on his way home, "but this time no crimes, only legal things."
He said he would not undertake such a flight again because his flight to Moscow, while daring, "was not responsible." Still, he acknowledged that he was pleased that it had dramatized his hopes for world peace and his belief that other private citizens must make their desires for peace heard in world capitals.
"I arrived as a child," he said. "Now I go home as an adult. It's really remarkable."
Asked why the Soviets released him early, he replied, "Humanity."
Rust flew the small, rented Cessna 450 miles from Helsinki, Finland, through some of the world's most heavily defended airspace, evaded Soviet jet fighters sent to intercept him, circled the Kremlin and buzzed its towers before landing on the cobblestones of Red Square.
He said he had been disappointed with the results of the Soviet-American summit meeting in Reykjavik, Iceland, in October, 1986, and was worried about the apparent deadlock in arms negotiations between the two superpowers and wanted to call attention to the world's desire for peace.
The extraordinary lapse in Soviet defenses led to the immediate ouster of Defense Minister Sergei L. Sokolov, along with the air defense chief and a number of their subordinates. It enabled Soviet leader Mikhail S. Gorbachev to put his own supporters into key military positions.
Rust, who was arrested while signing autographs half an hour after he landed, was convicted of "malicious hooliganism," endangering air safety and violating Soviet airspace and immigration regulations and sentenced last September to four years in a Soviet labor camp.
Many observers expected Rust to be freed quickly in the interest of Moscow's desire for better relations with West Germany, but prosecutors demanded an eight-year sentence to deter "any future adventures" by others. The court, in its one concession to the youth, sentenced him to four years in an ordinary prison rather than the harsher "strict regime."
"I realize that I have committed serious criminal offenses," he told the official Soviet news agency Tass on his release, "and the fact that the Presidium of the Supreme Soviet freed me from punishment before I served my term is an act of humanism.
"I think that this also attests to the overall improvement of relations between our two countries."
Smiling and looking fit, Rust told journalists that he had been well treated by Soviet authorities and had no complaints about his 14 months in Moscow's Lefortovo Prison.
In Bonn, a government spokesman said that West Germany welcomed the Soviet action, describing it as "a positive gesture" in advance of the scheduled visit of Chancellor Helmut Kohl to Moscow in October.
Hans-Dietrich Genscher, the West German foreign minister, had urged Rust's release in talks with Gorbachev and Eduard A. Shevardnadze, the Soviet foreign minister, during a weekend visit to Moscow.
Genscher said on West German television Wednesday: "The Soviet Union has shown its intention to solve humanitarian problems in a positive way. But I would like to add that nobody should feel encouraged by this fortunate outcome of the affair to try such an adventure once again."
West Germany is the Soviet Union's largest trading partner in the West, and Gorbachev regards Bonn as the key link in his concept of a "common European home" and in renewed efforts at reducing conventional armaments in central Europe.
Rust's mother, Monika, was overjoyed at the news of her son's release, although the family had no signals until Wednesday morning that he would be freed.
"I am happy, simply happy that Mathias is coming home," she told reporters at the family home near Hamburg.
"Mathias Rust Is Free!" the newspaper Frankfurter Rundschau declared in a banner headline after his release was announced in Moscow, but local prosecutors said Rust would be questioned on possible charges of endangering air traffic and fraud in connection with the rented aircraft.
His family has sold exclusive rights to his story to the West German magazine Stern, and both he and his parents refused to discuss the case for more than a minute or two.