London ? An American fighter pilot flying from an English air base at the height of the Cold War was ordered to open fire on a massive UFO that lit up his radar, according to an account published by Britain’s National Archives on Monday.

The fighter pilot said he was ordered to fire a full salvo of rockets at the UFO moving erratically over the North Sea – but that at the last minute the object picked up enormous speed and disappeared. The account, first published in Britain’s Daily Star newspaper more than 17 years ago and to this day unverified by military authorities, was one of many carried in the 1,500 pages the archives made available online.

The unnamed pilot said he and another airman were scrambled on the night of May 20, 1957, to intercept an unusual “bogey” on radars at a Royal Air Force Station Manston, an airfield at the southeastern tip of England about 75 miles from central London.

“This was a flying object with very unusual flight patterns,” the pilot said, according to a typed manuscript of his account mailed to Britain’s Ministry of Defense by a UFO enthusiast in 1988. “In the initial briefing it was suggested to us that the bogey actually was motionless for long intervals.”

Ordered to fly at full throttle in cloudy weather, the pilot said he was given the order to fire a volley of 24 rockets at the mysterious object.

“To be quite candid I almost (expletive) my pants!” the pilot said, saying he asked for confirmation – which he received.

Retired U.S. airman Milton Torres told Britain’s Sky News on Monday that he was the pilot and has spent 50 frustrating years attempting to uncover the truth of his mid-air encounter.

Speaking from his home in Miami, Torres said he never saw the UFO with his naked eye, but watched in awe as it appeared on his jet’s radar and sped off before he had a chance to fire.

Britain’s military said it had no record of the incident, according to the files. Neither did the U.S. military. The second pilot’s account, also included in the files, paints a somewhat different picture of events, saying there were not one but several “unknowns” and that he did not remember being contacted by anyone about staying quiet. He did not mention the targets’ size.

His name, like his colleague’s, was redacted from the files.

David Clarke, a UFO expert who has worked with the National Archives on the document release, said it was one of the most intriguing stories he had culled from the batch of files released Monday.

He said that the CIA once had a program intended to create phantom signals on radar – and that this may have been an exercise in electronic warfare. Whatever the case, Clarke argued that “there’s no doubt something very unusual happened.”