The UFO web page received 264,285 visits in just one day after it launched last month.
According to The National Archives, some 1.3 million files were downloaded in the first four days that the collection was online.
"It just shows the fascination in encounters of a third kind is very real. This launch exceeded our expectations and showcased our ability to deliver large-scale projects in the face of sustained web traffic," said David Thomas, chief information officer at The National Archives.
The records were put online after several requests from the general public under the Freedom of Information Act and cover the period from 1978 to 1987.
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