A man and his partner were travelling along the A50 when they spotted the object about 15 minutes into their journey.
The man noticed a “very bright light in the sky” which he said moved too slowly to be an aeroplane and at very low altitudes.
He said it had a small blinking light beneath it and flew over Carsington water at a height of around 100ft, before vanishing.
The incident happened on November 1, 2009 and was later reported to the Ministry of Defence’s UFO Desk. In his account - which has just been released by the National Archives, the man told officials that at this stage of his experience he "felt slightly unnerved.”