London: The men were air traffic controllers. Experienced, calm professionals. Nobody was drinking.

What they saw has never been explained. And they were so worried about losing their jobs that they demanded their names be kept off the official reports.

No one, they knew, would believe their claim that an unidentified flying object landed at the airfield they were overseeing in the east of England, touched down briefly, then took off again at tremendous speed.

But that's what they reported happening at 4 in the afternoon on April 19, 1984, at an unspecified small airport near the eastern coast of England. Their "Report of Unusual Aerial Phenomenon" is one of more than 1,000 pages of formerly secret UFO documents released yesterday by the National Archives.

The air traffic controllers, each with more than eight years on the job, describe how they were helping guide a small plane to a safe landing on runway 22 when they were distracted by a brightly lit object approaching a different runway without clearance.

"Everyone became aware that the object was unidentified," the report on the incident said. "SATCO (codename for a controller with 14 years experience) reports that the object came in 'at speed', made a touch and go on runway 27, then departed at 'terrific speed' in a 'near vertical' climb."

The incident is one of the more credible in the files because it was reported by air traffic controllers, said David Clarke, a UFO expert who has worked with the National Archives. "They were absolutely astonished," he said. "It was a bright, circular object, flashing different colours, and after it touched down it disappeared at fantastic speed." In one case, the pilot of a commercial plane crossing the Atlantic reported an object just 1.5 nautical miles from his wing. He speculated that it might be a meteor or a missile.

Although there are some unexplained cases, there is no reported instance in which Britain's Ministry of Defence found any evidence of alien activity or alien spacecraft, said Clarke, who nonetheless expects conspiracy theories about a UFO coverup persist.

Clarke said the documents released yesterday, dealing with the late 1970s and early 1980s, are the first batch of a series that will be made public in the next few years. The National Archives is releasing the files now because of numerous Freedom of Information requests seeking information about the government's UFO reports.

It was a bright, circular object, flashing different colours, and after it touched down it disappeared at fantastic speed."

UFO expert speaks on one incident.