West Freugh Incident, UK, 1957
Precis from Martin Shough's RADCAT:
According to a report in the Sunday Dispatch, April 7 1957, radar at RAF West Freugh had detected an unidentified target on April 4 at an altitude of 60,000' which was too large, too fast and too manoeuvrable to have been an aircraft. RAF intelligence ordered radar stations throughout the UK to be on 24 hour alert. An Air Ministry spokesman declined to make a detailed statement until a full report had been studied by experts, and Wing Commander Walter Whitworth, RAF West Freugh Commanding Officer, confirmed that the Ministry were taking the incident very seriously:
I have been ordered by the Air Ministry to say nothing about the object. I am not allowed to reveal its position, course and speed. From the moment of picking it up, it was well within our area. It was an object of some substance - quite definitely not a freak. No mistake could have been made by the [Ministry of Supply] civilians operating the sets. They are fully qualified and experienced officers.
There were sightings before and after the RAF West Freugh sighting, but none seemed to be connected with the radar tracking.