A Russian fighter jet tried to blast an RAF plane out of the sky over the Black Sea, US defence officials today revealed.
What would have been an act of war was narrowly avoided after the missile malfunctioned with Moscow's Su-27 fighter.
Britain's RAF RC-135 Rivet Joint was carrying a crew of up to 30 when the Russian pilot thought he had permission to fire, according to a secret US intelligence report.
Last year Defence Secretary Ben Wallace revealed some details about the incident and suggested the missile was launched by accident due to a "technical malfunction".
But it has come to light that the clash last year was far more serious than thought, after the secret documents were leaked online.
If a Russian missile had taken down the Rivet Joint, the UK and its Nato allies may have been compelled to go to war.
Two US defence officials commented on the files on Thursday in an interview with the New York Times.
It has emerged that the blundering Russian pilot mistakenly thought he had been given permission by a radar operator on the ground to fire at the British Rivet Joint and take it down on September 29.
The British plane had been flying through international airspace close to the Russian-occupied Crimea peninsula when it was met by a squadron on Su-27 fighters.
Known as a 'nuke-sniffer', it can detect radioactivity and is usually used to gather electronic transmissions and communications.
According to the report, the Russian pilot thought he had permission to fire, locked onto the spy plane and fired a missile.
One of the officials who was briefed on the encounter said it was "really, really scary" what happened.
But fortunately, the missile malfunctioned and avoided a potentially catastrophic situation.
Speaking at the time, Mr Wallace told MPs that the unarmed RAF jet was on a routine patrol in international airspace when it was tailed by the two Su-27 fighter jets.
The Defence Secretary then revealed that one of the Russian Su-27s then blasted a missile near the RAF plane during a 90-minute interaction off the coast of Ukraine.
Last weekend, the Washington Post reported that the incident was referred to as a "near-shoot down of UK RJ" in classified documents.
However, the Ministry of Defence has firmly denied the account of the incident revealed in the documents.
An MoD official told The Sun: "A significant proportion of the content of these reports is untrue, manipulated, or both.
"We strongly caution against anybody taking the veracity of these claims at face value and would also advise them to take time to question the source and purpose of such leaks.”
