Nice to see all the attention on the Twining Memo. As General and Chief of Staff of the United States Air Force, I think his opinion pretty much trumps everyone else's here regarding the reality of UFOs as structured craft.
j.r.
Well, you have your facts wrong again because Twining was not chief of staff when he wrote the memo. Secondly, Twining was offering an opinion based on reports. It was not a statement of fact as you seem to be thinking here. That is all it was and it was based on a lot of sketchy information. AMC wrote the memo because it was felt this needed further research and they suspected the source was soviet using German designs (i.e. like the Horton flying wing). If you actually read all the project SIGN documentation, you would see that this is exactly where they headed and this ended with the 1948 Top Secret Air study 203 which you can find at:
http://www.iufog.org/project1947/fig/1948air.htm
It is important to note that this TOP SECRET study states the following after evaluating all the information:
The origin of the devices is not ascertainable. There are two reasonable possibilities:
1. The objects are domestic devices, and if so, their identification or origin can be established by a survey of the launchings of airborne devices. Domestic flying wing type aircraft observed in various aspects of flight might be responsible for some of the reported flying objects, particularly those described as disks and rough cigar shapes. (See Appendices "C" and "D".) Among those which have been operational in recent years are the XF5U-1 ("Flying Flapjack") developed by Chance-Vaught, the Northrup B-35, and the turbo-jet powered Northrup YB-49. The present existence of any privately developed flying-wing type aircraft has not been determined but one such aircraft, the Arup tailless monoplane, was operational at South Bend, Indiana, prior to 1935.
2. Objects are foreign, and if so, it would seem most logical to consider that they are from a Soviet source.information on a number The Soviets possess of German flying-wing type aircraft such as the Gotha P60A, Junkers EF 130 long-range, high-speed jet bomber and the Horten 229 twin-jet fighter, which particularly resembles some of the description of unidentified flying objects (See Appendix "D"). As early as 1924 Tscheranowsky developed a "Parabola" aircraft, an all wing design, which was the outcome of considerable Soviet experimentation with gliders of the same general form. Soviet aircraft based on such designs might have speeds approaching trans-sonic speeds attributed to some flying objects or greater over-all performance assuming the successful development of some unusual propulsion device such as atomic energy engine.
I see no mention of alien spaceships here. They were assuming these were craft and the lack of any mention of an ET source in this TOP SECRET document indicates they were clueless as what to do.
This belief that they were craft of some kind waned as it became apparent that many of the sightings were simply misidentified objects. Therefore, there was a shift in the approach by the time the final report for SIGN was written it was not even clear if any real craft (other than those misperceived) were even seen:
No definite evidence is yet available to confirm or disprove the actual existence of unidentified flying objects as new and unknown types of aircraft.
http://www.nicap.org/docs/SignRptFeb1949.pdf
The bottom line here is you are taking Gen. Twinings words out of context and trying to fit it into your own belief system.