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UFOs in History»
Air Ministry investigation
Sewart’s report was completed on 27 January 1947 but is missing from the Public Record Office file where it is listed as an attachment to the station logbook. Summarising its contents, Squadron Leader Cruwys said ‘evidence appears to be strong’ that the unidentified tracks were caused by radio-sonde balloons released from Downham Market in Norfolk. Downham was a World War Two bomber airfield that was used by the USAAF’s 8th Weather Squadron in 1947 for the release of balloons for the study of the upper atmosphere. It can be inferred, in the absence of his original report, that Sewart had matched the release of radio-sondes with Charlie’s movements. He may have decided that balloons trapped by turbulent upper-air currents that were developing over southern England had been blown back towards their launch station in Norfolk. Their movements whilst trapped in upper air currents had taken radar operators by surprise and had led to the scramble of aircraft.
However statements made by the Air Ministry, firstly to the Press in April 1947 and again to the USAAF in July, flatly contradict Sewart’s conclusions and imply that the Air Staff remained open-minded about the identity of Charlie. Even Group Captain Kent’s account of the ‘unidentified aircraft’ ended with this comment: “I mentioned that a burst met balloon was a possibility, deduced afterwards from its ‘behaviour’...but at that time these things [flying saucers] were unheard of and not taken at all seriously.” 
Other expert opinion attributed the unusual radar blips to freak weather conditions. Operation Charlie coincided with the arrival on 24 January 1947 of a deep cold weather front over southern England, a fact that did not escape attention at the Air Ministry. Before the 1950s, knowledge of the role played by freak weather conditions in the production of ‘false’ echoes nick-named ‘angels’ was in its infancy. Although little understood at the time, the astronomer Dr J. Allen Hynek, who was employed as a consultant to the US Air Force Project Blue Book, believed “atmospheric inversion effects” were the most likely explanation for the English ‘ghost plane’ reports.  This explanation is challenged in a technical assessment of the evidence by Martin Shough (see Appendix).
The Air Ministry may have decided it could dismiss the majority of the mysterious blips on its screens as balloons, but in July when the US authorities began to investigate reports of ‘flying saucers,’ the RAF continued to list the North Sea incident as ‘unexplained’. Dr Hynek’s notes on this case read: “The object observed here was obviously not astronomical. From the information given, it appears that this was definitely an aircraft..”  This raises an obvious question: if it was an aircraft, then where was it from?
According to Geoff Easterling the RAF’s prime suspect was a Russian intruder aircraft flying from a base in occupied Germany. However, if the speed and performance of the target tracked on 16 January 1947 recalled by David Richards (and apparently confirmed by the contemporary press reports) are correct, this becomes an unlikely proposition. Soviet aircraft were unreliable at long range, and it seems inconceivable that an intruder mission would risk an overflight of UK territory in such a reckless fashion during a period of extreme and unpredictable weather. In addition, Soviet versions of the US B-25 were capable of a maximum speed of 250-300 kts, a figure well within the interception ratio of the RAF Mosquito.
It remains unclear if further unidentified radar blips
continued to plague the RAF as the ‘ghost plane’ era moved
into the age of the ‘flying saucer.’ Entries in the logbooks
of radar stations on the south coast of England describe a number of similar
incidents during April and May, 1947. One entry from the logbook of RAF
Rye, a CH station in Kent, reads: “...the most noteworthy track
plotted was an unidentified aircraft which was plotted from 52 miles out
to the maximum range of 186 miles.”  Group Captain Kent recalls:
“I have no other sorties listed in my log books as ‘scramble
intercepts’ such as that of 17 January 1947, but I did fly a few
others against ‘odd’ and ‘strange’ blips as seen
by ground radars in an around East Anglia. I flew at least one in daylight
but nothing was seen.” 
The newspaper compared the ghost plane mystery with the reports of phantom German Zeppelins that had circulated before the outbreak of World War I and observed: ‘It seems to be established that it is only at times of peculiar stress that the public is in the psychological state to receive and circulate such stories.’ The practical steps to solve the mystery were clear: