For decades the MoD has been recording sightings of UFOs and, in some cases, calling in its experts to examine the reports in detail.
In Northamptonshire, according to the files released under the Freedom of Information Act, people have reported strange objects in the sky on 27 occasions since 1998.
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Although defence officials say they only examine UFO reports to establish whether another country has breached UK airspace, letters between MoD officials and members of the public reveal officials remain "totally open-minded" about the existence of UFOs.
The latest reported sighting in Northampton was in the evening of September 17 in 2003 when a person saw "two small, star-size objects that were dark orange or rust colour, which were followed by another two, doing manoeuvres".
Three years earlier three objects, larger than a plane, which were shaped rectangular, square and hook, were spotted above Towcester and Brackley. The person who reported the UFOs said they were orange and brighter than Venus.
Among the hundreds of reported sightings in the UK over the last decade, dozens have come from military personnel, civil pilots and police officers.
On the night of November 23 in 2000 a policeman reported seeing a large round pink object above the Eastern Districts of Northampton. The officer added that a handful of circular objects were attached to it.
A spokesman for the MoD said the military only examined a sighting if it might be a potential threat: "The MoD examines reports solely to establish whether UK airspace may have been compromised by hostile or unauthorised military activity," he said.
"If required, sighting reports are examined with the assistance of the department's air defence experts."
Despite perennial claims of alien abductions and cover-ups, MoD officials say there is no evidence to substantiate the existence of UFOs.
The MoD states: "We believe that rational explanations, such as aircraft lights or natural phenomena, could be found for them if resources were diverted for this purpose, but it is not the function of the MoD to provide this kind of aerial identification service."
