"I have interviewed five of the CAA personnel involved in this case and four of the commercial airline pilots involved, I have checked the radiosonde data against well-known radar propagation relations, and I have studied the CAA report subsequently published on this event. Only an extremely lengthy discussion would suffice to present the serious objections to the official explanation that this complex sighting was a result of anomalous radar propagation and refractive anomalies of the mirage type. The refractive index gradient, even after making allowance for instrument lag, was far too low for "ducting" or "trapping" to occur; and, still more significant, the angular elevations of the visually observed unknowns lay far too high for radar- ducting under even the most extreme conditions that have ever been observed in the atmosphere. Some of the pilots, directed by ground radar to look for any airborne objects, saw them at altitudes well above their own flight altitudes, and these objects were maneuvering in wholly unconventional manner. One crew saw one of the unknown luminous objects shoot straight up, and simultaneously the object' s return disappeared from the ARTC scope being watched by the CAA radar operators. The official suggestion that the same weak (1.7"C) low-level "inversion" that was blamed for the radar ducting could produce miraging effects was quantitatively absurd, even if one overlooks the airline-pilot sightings and deals only with the reported ground-visual sightings".

Dr. James E. McDonald, Senior Physicist at the Institute of Atmospheric Physics at the University of Arizona

Diagram of the UFOs tracked by Washington's National Airport radar scope on July 20, 1952. At A, 7 objects approach the Nation's capital from the south. At B, some are seen over the White House and Capitol. At C, they appear over Andrews Air Force Base. At D, one UFO tracks an airliner. At E, one is seen to make a sharp right-angular turn.

Source: UFOs - A Pictorial History From Antiquity to the Present, by David C. Knight. (McGraw Hill Book Co., 1979.)

Though the major Washington sightings occurred over the weekends of July 1920 and July 26-27, 1952, sporadic reports and trackings were recorded into mid-August. Here, the black dots indicate unidentified targets tracked on the radar screen at Washington National Airport on August 15

"..become most active around the planes we saw on the scope. . . . They acted like a bunch of small kids out playing. It was helter-skelter as if directed by some innate curiosity. At times they moved as a group or cluster, at other times as individuals over widely-scattered areas. . . .

There is no other conclusion I can reach but that for six hours on the morning of the 20th of July there were at least 10 unidentifiable objects moving above Washington. They were not ordinary aircraft. I could tell that by their movement on the scope. I can safely deduce that they performed gyrations which no known aircraft could perform. By this I mean that our scope showed that they could make right angle turns and complete reversals of flight. Nor in my opinion could any natural phenomena account for these spots on our radar. Neither shooting stars, electrical disturbances nor clouds could either. Exactly what they are, I don’t know".

"As a result of several trips to project Bluebook,I´ve had an opportunity to examine quite carefully and in detail the types of reports that are made by Bluebook personnel.In most cases, I have found that theres almost no correlation between so-called "evaluations and explanations" that are made by Bluebook and the facts of the case...
There are hundreds of good cases in the Air Force files that should have led to top-level scientific scrutiny of this problem,years ago,yet these cases have been swept under the rug in a most disturbing way by Project Bluebook investigators and their consultants."

Dr James McDonald -Senior physicist at the Institute for Atmospheric Physics and professor in the Department of Meteorology at the University of Arizona