Shortly after 9 a.m. Moscow time on April 12, 1961, Soviet cosmonaut Yuri Gagarin rocketed straight into the history books when he became the first man to fly into outer space. The unassuming 27-year-old pilot and engineer, who made only one statement during his one hour, 29 minutes spent orbiting the Earth a single time (“Flight is proceeding normally; I am well.”), instantly became an international celebrity on his return. Then on March 27, 1968, he and another pilot were killed when their two-seater aircraft crashed during a routine training flight. Discover the story behind the mystery surrounding his death, including surprising details that emerged only decades later.

Becoming the First Man in Space
The son of a carpenter, Yuri Alekseyevich Gagarin was born in the village of Klushino in Smolensk, Russia in 1934. At 16, he moved to Moscow to apprentice as a foundry man in a metal works, but soon transferred to a technical school in Saratov. There, Gagarin joined a flying club and took to the skies for the first time. He graduated from the Soviet Air Force cadet school in 1957, and began serving as a fighter pilot. He married his wife, Valentina, that same year; they went on to have two daughters.

In 1960, Gagarin was selected along with 19 other candidates for the Soviet space program. The program winnowed the cosmonauts down to two—Gagarin and fellow test pilot Gherman Titov—as finalists to make the program’s first flight into space. Some thought Gagarin made the cut due to Soviet premier Nikita Khrushchev’s preference for his more modest background (Titov was the son of a schoolteacher).

At 9:07 a.m. on April 12, 1961, when Gagarin’s Vostok 1 spacecraft lifted off from Baikonur cosmodrome, he uttered the surprisingly informal, immediately iconic exclamation “Poyekhali!” (Translation: “Let’s go!”) His flight, a single orbit around the Earth, was uneventful, but the landing ended in near-disaster when the cables joining the Vostok’s descent module and service module failed to separate properly, causing massive shaking as the spacecraft reentered Earth’s atmosphere. Gagarin ejected before landing, parachuting down safely near the Volga River.

Yuri Gagarin, portrait. (Credit: rps/ullstein bild/Getty Images)
Yuri Gagarin, portrait. (Credit: rps/ullstein bild/Getty Images)

Hero of the Soviet Union
Gagarin became an international celebrity, toured the world and was showered with honors by his country. Krushchev’s government awarded him the Order of Lenin, and named him a Hero of the Soviet Union. Gagarin’s triumph was a painful blow to the United States, which had scheduled its first space flight for May 1961. What’s more, a U.S. astronaut wouldn’t match Gagarin’s feat of orbiting the Earth until February 1962, when astronaut John Glenn made three orbits in Friendship 7. (By that time, Titov had already become the second Soviet to make it to space, making 17 orbits of Earth over 25 hours in Vostok 2 in August 1961.)

Gagarin struggled with drinking on the heels of his fame, but by the late 1960s had returned to his training. He was chosen as back-up pilot for the ill-fated Soyuz 1 mission (in which two Soviet spacecraft were supposed to rendezvous in space), and watched in horror as his friend Vladimir Komarov died when his parachutes failed to open on re-entry in April 1967.

A Hero’s Tragic End
Less than a year later, on March 27, 1968, Gagarin himself was killed when a two-seater MiG-15 fighter jet he was flying with Vladimir Seryogin, crashed outside a small town near Moscow during a routine training flight. Gagarin’s ashes were placed in a niche in the Kremlin wall, while his hometown of Gzhatsk was renamed Gagarin in his honor.

An official investigation into the accident concluded that Gagarin swerved to avoid a foreign object—such as a bird or weather balloon—sending the plane into a tailspin that ended with its crash into the ground. But many aviation professionals viewed this conclusion as implausible, and rumors continued to swirl around the crash. Some thought Gagarin might have been drinking, or that he and Seryogin might have been distracted by taking photographs from the plane’s window. Others suggested a cabin pressurization valve could have failed, causing both pilots to suffer hypoxia. More outlandish theories included sabotage for political motives, suicide or even collision with a UFO.

The Truth, Declassified
Gagarin’s friend and fellow Russian cosmonaut, Alexei Leonov, was in the area on the day of the crash and served (along with Gherman Titov) on the board that investigated the accident. In 2013, Leonov announced on the Russia Today TV network that another report on the crash, recently declassified, confirmed the real story: A second plane being tested that day, an Su-15 jet, mistakenly flew far lower than its planned altitude of 33,000 feet, instead passing close to where Gagarin’s plane had been flying, around 2,000 feet. Such a large aircraft would be able to roll over a smaller one (like the MiG-15) in its wake if the two planes came too close to each other.

After running various computer simulations, the report concluded that the only viable explanation for the crash was that the Su-15 flew too close to Gagarin’s plane that day, flipping it and forcing it into an unrecoverable spiral dive towards the ground. When asked why the report remained classified for so long, Leonov replied “My guess would be that one of the reasons for covering up the truth was to hide the fact that there was such a lapse so close to Moscow.” Leonov agreed not to identity the test pilot of the Su-15, who was 80 years old at the time, as a condition of being able to go public with the truth nearly five decades after the history-making cosmonaut’s fatal crash.