In another careful analysis of a dubious element of UFO history, Andy Roberts says:
We have at least one outright hoax in foo-fighter lore. For years rumours had been flying round that the Germans had been fully aware of the foo-fighter phenomenon and that they had a special study group formed to look into the problem under the name of "Project Uranus", backed by a shadowy group by the name of Sonderbüro 13. This was first detailed in La Livres Noir De Soucoupes Volantes (The Black Book of Flying Saucers - 1970) by French ufologist Henry Durrant. The rumour spread in Europe and eventually took physical form in the English language in Tim Good's acclaimed book Above Top Secret where it is used to help substantiate further vague rumours of an Anglo/American foo-fighter study. Good had not checked his facts and had in fact just copied the information direct from Durrant's book.
When I checked this out with Durrant he informed me that the whole "Project Uranus" affair was a hoax which he had inserted in his book precisely to see who would copy it without checking. The hoax apparently had been revealed in France some years before but hadn't percolated its way through to English speaking ufologists. Perhaps other foo hoaxes await discovery. 
The 'Schweinfurt Raid'
This tale involves, well, little flying saucers, in a B-17 raid on October 14 1943, aimed at the ball-bearing factories at Schweinfurt in Germany. It was publicised by popular US author Frank Edwards in Flying Saucers - Here and Now  in 1967, but I understand that the original glamourised version comes from one Martin Caidin, in his book Black Thursday, published in 1960. Caidin reports that :
During the bomb run of several groups, starting at about the time the Fortresses approached the Initial Point, there occurred one of the most baffling incidents of World War II, and an enigma that to this day defies all explanation." "As the bombers of the 384th Group swung into the final bomb run after passing the Initial Point, the fighter attacks fell off. This point is vital, and pilots were queried extensively, as were other crew members, as to the position at that time of the German fighter planes. Every man interrogated was firm in his statement that "at the time there were no enemy aircraft above."
At this moment the pilots and top turret gunners, as well as several crewmen in the Plexiglas noses of the bombers, reported a cluster of discs in the path of the 384th's formation and closing with the bombers. The startled exclamations focused attention on the phenomenon and the crews talked back and forth, discussing and confirming the astonishing sight before them.
The discs in the cluster were agreed upon as being silver colored, about one inch thick and three inches in diameter. They were easily seen by the B-17 crewmen, gliding down slowly in a very uniform cluster." "And then the `impossible' happened. B-17 Number 026 closed rapidly with a number of discs; the pilot attempted to evade an imminent collision with the objects, but was unsuccessful in his maneuver. He reported at the intelligence debriefing that his right wing "went directly through a cluster with absolutely no effect on engines or plane surface.
The intelligence officers pressed their questioning, and the pilot stated further that one of the discs was heard to strike the tail assembly of his B-17, but that neither he nor any member of the crew heard or witnessed an explosion." "He further explained that about twenty feet from the discs the pilots sighted a mass of black debris of varying sizes of clusters of three by four feet." "The SECRET report added: `Also observed two other A/C flying through silver discs with no apparent damage. Observed discs and debris two other times but could not determine where it came from.
No further information on this baffling incident has been uncovered, with the exception that such discs were observed by pilots and crew on missions prior to, and after, Mission 115 of October 14, 1943. 
Caidin's account is footnoted "1 Memorandum of October 24, 1943, from Major E.R.T. Holmes, F.L.O., 1st Bombardment Division, Reference FLO/IBW/REP/126, to M.I.15, War Office, Whitehall, London, SW (copy to Colonel E.W. Thomson, A-2, Pinetree)", but Andy Roberts actively investigated the reference, and reports that
...a letter to the M.O.D at their Air Historical Branch 5 came to nothing, suggesting that either of the documents may be held at the Public Records Office at Kew, London. A professional researcher was despatched to try to find the document. She searched all relevant Air Force records available (some are still bound by various `rules' with embargoes on viewing of up to 100 years) but could find nothing, despite the help of staff there and noting that "the reference FLO etc. does not correspond with any references at the record office.
In the USA, Dennis Stacy (then MUFON UFO Journal editor) had taken an interest in the case and followed up several leads, aided by the Freedom of Information Act. Firstly the A.F. Historical Research centre at Maxwell AFB searched their 8th A.F. files but could come across no documentary record of the event (interestingly enough I tried the same source and whilst they gave me squadron histories of the 415th Night Fighter squadron and their documented foo-fighter sightings, they could provide nothing on the Schweinfurt raid -- odd if the Schweinfurt events were real).
The National Archives (Washington) searched their files but drew a blank. A letter written to French researcher J. M. Bigorne from the National Archives stated "A search in records of the United States Strategic Bombing Survey (USSBS), European War, Target Damage File, 11a (2606), Schweinfurt, failed to disclose any documentation or information regarding little flying discs by B-17 pilots." All this presents us with a quandary. If the Archives are quite free about some foo-fighter info why, if it exists at all, should they be that bothered about concealing the Schweinfurt material? So far three independent researchers over the past ten years have had the same answer -- none of the flight records for that day record the event in Caidin's book. As I have seen other pilots' logs which mention unusual UFO-type sightings during missions it would be inconceivable for at least a few aircrew on that raid to have mentioned it even in passing - especially as in this case it was obviously something of an item at de-briefing.
Letters in numerous aircrew magazines (UK & US) requesting info on the raid were placed and despite many replies no-one knew anything. Aviation writers Martin Middlebrook and Chaz Bowyer who have written many highly detailed books about the air war, and have interviewed thousands of aircrew, wrote to say they had never heard of the incident, despite having had foo-fighters mentioned to them in other contexts.
Dennis Stacy contacted the 384th Bombing Group survivors association and with no account of the UFO sighting forthcoming from them was put onto General Theodore Ross Milton who led the raid that day and went in first with the 91st Group Formation. He wrote; "I don't recall seeing black discs or hearing about any strange phenomena from any of my group." 
Roberts and Stacy pursued the source further.
Martin Caidin, originator of the rumour also presents problems. His book Black Thursday was first published in 1960 and yet quotes an alleged SECRET report. How did he get hold of it then and why has it not been seen since? As for Caidin himself, several people have tried to get in touch with him without success. Both myself and (then) MUFON Journal editor Dennis Stacy have tried to track him down via his publishers and a UFO magazine he has written for, but to no avail. He last appeared in the dodgy US magazine UFO Universe where he was featured on the front page as having 'chased bogies at 20,000 feet,' (an astonishing spectacle no doubt!), but whilst the article gave details of UFOs he'd seen post-WWII, government film of UFOs, cover-ups, and you name it (along with mucho promotion for his many books, including UFO based novels) the Schweinfurt raid was never mentioned. Funny that, really." 
However, with the terrier-like tenacity for which he is renowned, Roberts kept searching, and in September 2000 finally found, in the Records Office at Kew:
The document which Caidin obviously based his account on. It reads as follows. All spelling and punctuation is in the original. The file in which the document can be found is: AIR 40/464. At the top right of the document is a rubber stamp giving details of circulation to:
1. Col Kingman Douglas
2. A.I.3. ? (W/Cdr Smith)
3. A.I. 2. ? (W/Cdr Heath)
(Author's note: the ? refers to a squiggle or letter I cannot decipher, although it could well be 'to'. Also the background of the stamp on which the above was written says:
Received 17 Oct 1943
Copies sent to A.I.8 (USA))
The rest of the document is as follows:
EKG. TELEGRAM EN CLAIR 4112
Recd. AMCS. 171129a hrs Oct.43
To- OIAWW, OIAJX, OISHL, HBC, AMY.
From - OIPNT
IMPORTANT - CONFIDENTIAL
8 BC 0-1079-E
Annex to Intelligence Report Mission Shweinfurt 16 October 1943
306 Group report a partially unexploded 20mm shell imbedded above the panel in the cockpit of A/C number 412 bearing the following figures 19K43. The Group Ordnance Officer believes the steel composing the shell is of inferior grade. 348th Group reports a cluster of disks observed in the path of the formation near Schweinfurt, at the time there were no E/A above. Discs were described as silver coloured - one inch thick and three inches in diameter. They were gliding slowly down in very uniform cluster. A/C 026 was unable to avoid them and his right wing went directly through a cluster with absolutely no effect on engines or plane surface. One of the discs was heard striking tail assembly but no explosion was observed. About 20 feet from these discs a mass of black debris of varying sizes in clusters of 3 by 4 feet. Also observed 2 other A/C flying through silver discs with no apparent damage. Observed discs and debris 2 other times but could not determine where it came from.
P.R. & A.I.6.
A.I.3. (USA) (Action 2 copies)
Presumably Caidin must have seen a copy of this document from one of the American recipients .. The Rubber stamp clearly states it was received on 17 October, pre-dating Caidin's reference by seven days. But the sheer number of channels through which documents went could be the reason for this confusion and now the original document has been located I don't think we need get hung up on the original reference any more. I have found no record of most of the personnel listed. However a Squadron Leader Heath was involved in the UK's investigations of the Scandinavian 'ghost rockets' in 1946.
At least we now know Caidin's reference exists! Besides that there is little to say really. The objects reported are intriguing but not completely mystifying. There were many types of flak being used by the Germans in W.W.II and several files in the PRO refer to coloured flak, flak which threw off unusual fragments, and so on. This explanation is made more likely by the fact that the 'F.L.O.' in Caidin's reference stands for 'Flak Liaison Officer', at least suggesting that the Air Ministry were treating it within a flak context. The objects could also have been some kind of 'window' dropped by the Germans in an attempt to disrupt radar or radio communication among air crew. The explanation as to what the small objects were is now more of a task for the air historian than it is for the ufologist. What is clear from the original account is that the discs, whilst unusual, were clearly not any type of 'craft', under intelligent or purposeful control or dangerous to the air craft or crew.
In my opinion these objects do not belong in the category of sightings referred to as 'foo-fighters', both by their physical description and by their behaviour and characteristics. Although often lumped in with foo-fighter reports they are clearly different. This story has been a staple of UFO writers for the past three four decades. Now we have further clarification and I believe that this particular mystery is more or less laid to rest.
Andy Roberts is more charitable to Caidin's exaggerated and redefined version of the report than I, but Caidin is nowhere near as foolish as those who put together the second block (1998 release) of 'Majestic 12' documents. Nevertheless, Nick Redfern and Jonathan Downes present a copy of a section of these silly documents, which says:
Aerial interference with military aircraft has demonstrated the ability to observe our air operations in war and peacetime conditions. During the war over 900 near-miss incidents were reported by allied pilots and crews in all theater of operations. One of the most dramatic near-miss encounters occurred on 14 October 1943, 8th AF Mission 115 over Schweinfurt, Germany, B-17 crews reported many formations of silvery discs flying down into the B-17 formations. Several times during the bombing mission, large objects were seen following the discs descent into the formations. Unlike previous reports, no engine failures or airframe damage was reported. After the surrender of Nazi Germany, GAF fighter pilots were interrogated by AF intelligence concerning Mission 135. GAF did not have any aircraft above our bombers at that time. 
I've never found the whole 'MJ-12' idea credible, but at least the first release of documents was prepared with sufficient care to provoke meaningful discussion. This ridiculous exaggeration of an already elaborated tale makes the second release of documents look absurd. I would also point out that the Nazi UFO mythos and MJ-12 are essentially incompatible: if the Americans had already gained the ability to build high-performance flying discs from the Germans, why would they have become so excited about crashed ET discs? And why didn't all those portentous 'first-release' documents mention them at all?
The Massey Project
Redfern and Downes continue to publicise another claim made by Frank Edwards, just before his account of the Schweinfurt Raid. Despite being aware of the negative outcomes of research conducted by both Andy Roberts and Tim Good, they say:
As far as the British Government is concerned, there is strong evidence to show that extremely rigorous investigations were made into the Foo Fighter phenomenon by an elite team of Air Ministry and Royal Air Force operatives. 
They quote Edwards
As early as 1943, the British had set up a small organisation to gather information on these objects. It was under the direction of Lieutenant General Massey, and it had been inspired to some extent by the reports of a spy who was in reality a double agent, working under the directions of the Mayor of Cologne. He had confirmed that the Foo Fighters were not German devices, which of course the British knew they were not. The British Air Ministry, in 1966, told me that the Massey project was officially terminated in 1944. Perhaps it is only coincidence that the double agent was exposed and executed in the spring of 1944. 
Three problems arise immediately. Tim Good has established, from a dependable source, that there was no Lieutenant General Massey. Almost all the foo fighter reports date from 1944 onwards, so it's not clear why "extremely rigorous investigations" should start in 1943 and end in 1944. And what on earth was a spy doing being controlled by the Mayor of Cologne? On the evidence, the 'Massey Project' sounds like a complete, and deliberate, fabrication.
Crashed saucers and back-engineering
Nick Redfern makes a great deal of limited evidence in suggesting that there has ever been one extra-terrestrial flying craft crash on Earth since 1900, let alone more than one. He has not, however, been unwilling to suggest that the Nazis had access to one or more crashed flying saucers, and back-engineered technology from them. This, supposedly, was how they were able to develop such sophisticated flying discs! Of course, he is not alone in making suggestions of this kind, but I hardly need point out that when the evidence suggests that Germany had no sophisticated flying discs, then there is nothing to explain. Anyway, Redfern concludes from the rather desperate, and generally quite implausible intelligence reports that he has collected
If . . the data related in official FBI memoranda of the 1940s, 1950s and 1960s is accurate, how were the Nazis able to develop technology that, years later, was still defying America's finest" As I will later show, there are firm grounds for believing that a number of extra terrestrial vehicles crashed to earth on US soil in the late 1940s. Is it stretching the bounds of possibility to speculate that a similar event may have occurred on Nazi territory several years previously? If such an event did take place, and the Germans were able to grasp the rudiments of the technology, this would perhaps go a long way towards explaining their pressing desire to perfect a man-made flying saucer. The truth may ultimately turn out to be far stranger than has previously been realised. 
Well, yes, it really does stretch the bounds of possibility, but that doesn't stop Corso from reporting, in 'The Day After Roswell', what he and General Twining had wondered about after inspecting the crashed saucer at Roswell:
At the very least, Twining had suggested, the crescent-shaped craft looked so uncomfortably like the German Horten wings our flyers had seen at the end of the war that he had to suspect the Germans had bumped into something we didn't know about. And his conversations with Wehrner von Braun and Willy Ley at Alamogordo in the days after the crash confirmed this. They didn't want to be thought of as verruckt but intimated that there was a deeper story about what the Germans had engineered. No, the similarity between the Horten wing and the craft they had pulled out of the arroyo was no accident. We always wondered how the Germans were able to incorporate such advanced technology into their weapons development in so short a time and during the Great Depression. Did they have help? With an acceleration capability and maneuverability we'd never seen before, this craft would keep American aircraft engineers busy for years just incorporating what you could see into immediate designs. 
While we're in a corner of reality that accepts the reality of the Roswell crash, and its cargo of dead or possibly living entities, I have to mention the analysis of Polish writer Zbigniew Blania-Bolnar in Alien Encounters for April 1998. Telling us that " . . the post-war American Army had at its disposal a considerable number of V2 rockets, several V3 and V4 prototypes, and about 30 kugelblitzes of different kinds", he concludes that the dead entity in the Laredo crash (the Laredo crash?) was "a laboratory monkey used by the Air Force in a secret experiment." And, of course, "if a tested kugelblitz crashed at Laredo, then a similar object could have crashed at Roswell." 
None of the suggestions that the Germans back-engineered crashed alien craft pre-date the Lazar and Lear back-engineering stories. Three more have come to light already. In her book 'Sightings: UFOs' Susan Michaels reports that writer Jan Van Helsing (a contact of the inner circle of the 'Montauk Project')
"describes the discovery of a crashed saucer in the Black Forest in 1936 and says that this technology was taken and combined with the information the Vril Society had received through channeling and was made into a further project called the Haunebu." 
There is also a report of a crash in Italy in 1933, the details and information of which were made known to Mussolini, and which assisted Belluzzo in his design and development.  And at the 'Gdansk UFO-Marathon' in October 1997, it was announced that there had been a crash in Poland in the summer of 1938, in Czernica. Evidence and wreckage recovered from the crash was seized by Nazi Germany after the invasion of Poland the next year, and the information so gathered was used in the building of the 'Haunebu' and 'Vril' craft.  The current popularity of back-engineering is such that I expect to see more such reports.