Yuri Gagarin air crash details revealed by fellow cosmonaut Alexey Leonov

New details have emerged about the air crash on 27 March 1968 that killed the first man in space – Yuri Gagarin.

Fellow cosmonaut Alexey Leonov claims an “unauthorized” plane flew too close to Yuri Gagarin’s fighter jet, sending it into a spin.

Yuri Gagarin and his flight instructor Vladimir Seryogin died when their MiG-15 went down near the town of Novoselovo, about 90 km (56 miles) from Moscow.

Secrecy surrounding the crash has led to vigorous speculation down the years.

A government investigation of the accident (which Alexey Leonov was part of) concluded that the MiG tried to avoid a “foreign object” – such as geese, or a hot air balloon.

On the conclusions of this original investigation, Alexey Leonov said: “That conclusion is believable to a civilian – not to a professional.”

In an interview with Russia Today, the cosmonaut – who, in 1965, became the first person to walk in space – claimed he had been permitted to share a declassified report showing that a Sukhoi fighter jet flew too close to Yuri Gagarin’s MiG, disrupting its flight.

“We knew that a Su-15 was scheduled to be tested that day, but it was supposed to be flying at the altitude of 10,000 metres or higher, not 450-500 metres. It was a violation of the flight procedure,” he told the television channel.

Alexey Leonov says Yuri Gagarin’s plane went into a spiral at 750 km/h following the close pass by the jet.

However, Alexey Leonov declined to name the Sukhoi pilot.

“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,” he explained.

The cosmonaut had already hinted in his 2004 book Two Sides of the Moon that a Sukhoi jet may have been flying below its minimum allowed altitude. Alexey Leonov had been flying a helicopter in the same area on the day of the accident and heard “two loud booms in the distance”.

Many other theories have been advanced in the ensuing years, including one that a cabin air vent was accidentally left open in Yuri Gagarin’s aircraft by the previous pilot. This, the theory claims, would have led to oxygen deprivation for the crew.

Yuri Gagarin became the first person to journey into space on 12 April 1961, when his Vostok spacecraft completed a single orbit of Earth.