LONDON — The men were air traffic controllers. Experienced, calm professionals. Nobody was drinking. But they were so worried about losing their jobs that they demanded their names be kept off the official report.

No one, they knew, would believe their claim an unidentified flying object landed at the airport they were overseeing in the east of England, touched down briefly, then took off again at tremendous speed. Yet that's what they reported happened at 4 p.m. on April 19, 1984.

The incident is one of hundreds of reported sightings contained in more than 1,000 pages of formerly secret UFO documents being released today by Britain's National Archives. It is one of the few that were never explained.

The air traffic controllers' "Report of Unusual Aerial Phenomenon" was filed from an unspecified small airport near the eastern coast of England.

The men, each with more than eight years on the job, described how they were helping guide a small plane to a 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," their report said. "SATCO (code name 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 newly public files because it was reported by air traffic controllers, said David Clarke, a UFO expert who worked with the National Archives on the document release.

"They were absolutely astonished," he said. "It was a bright, circular object, flashing different colors, and after it touched down it disappeared at fantastic speed. The report comes from very qualified people, and it's one of the few that remained unexplained."

But while there are some unexplained cases in the papers, there is no reported instance in which the Ministry of Defense found any evidence of alien activity or alien spacecraft, said Clarke, who nonetheless expects conspiracy theories about a UFO cover-up by the British defense establishment to persist.

"The Ministry of Defense doesn't have any evidence that our defenses were breached by alien craft," Clarke said. "They never found one, no bits of one. That's all we can say," he added.

Clarke said the released documents, dealing with the late 1970s and early 1980s, are the first batch in a series that will be made public in the next few years.