Date: July 24, 1952
 Location: Near Carson Sink, Nevada

This object,  similar to the one discussed below,  was  observed
30 years later at Floyd Knobs,  Indiana,  on  March 4, 1990.   It
still hasn't shown up in any world military inventory.

Michael David Hall:
One such case had to be believed because it came from extremely reliable witnesses. Their sighting occurred over Carson Sink, Nevada. It involved two competent observers who were both Air Force officers. These witnesses, Lieutenant Colonel John L. McGinn and Lieutenant Colonel John R. Barton, were also intimately familiar with every type of aircraft or missile in the world at that time. For that reason their sighting drew great attention at both ATIC and the Pentagon when it surfaced. The incident took place while on board a twin engine B-25 bomber that they had requisitioned for a cross-country flight beginning from Hamilton AFB (formerly Hamilton Field). After take off they were headed for Colorado Springs on a very clear day with unlimited visibility. Such perfect flying conditions are appreciated by any veteran flyer, especially the two lieutenant colonels who were looking forward to a smooth ride and the chance to take in some beautiful scenery. While over the Sierra Nevada, McGinn and Barton did see some amazing terrain but soon saw something even more spectacular.

Between Sacramento and Reno they entered “Green 3,” the airway’s version of a highway into Salt Lake City. At 3:40 P.M. MST while at 11,000 feet over the Carson Sink area of Nevada, the pilots spotted three aircraft ahead of them and to their right. At first the lieutenant colonels assumed these must be F-86 jet fighters. The “bogies” were moving much like the new jets - although something just didn’t add up. If they were F-86s, they should be lower in accordance with civil air regulations, and it also appeared odd to see military jets fly in what appeared to be a perfect V formation.

In short order their B-25 closed in on the objects, close enough for a better look. The pilots then immediately realized they weren’t F-86s at all, but what were they? Each craft appeared very bright silver in color with a delta wing-like airfoil. They thought these couldn’t be a new type of delta jet because they had no tails or pilot’s canopies. The craft all displayed a clean upper triangular wing with a definite ridge running from nose to tail. Before McGinn and Barton fully grasped the fantastic sight before them, the strange objects made a left bank and zoomed within 400 to 800 yards of their B-25, an uncomfortably short amount of space in the air. Their speed was estimated by the men to be at the very least three times that of any conventional jet then flying! Yet after four short seconds the hair raising maneuver was over and the UFOs were gone.

As soon as McGinn and Barton landed at Colorado Springs they were on the phone to Air Defense Command Headquarters. When they learned that no civilian or military aircraft were anywhere near them at 3:40 P.M., the magnitude of their sighting finally sunk in. McGinn and Barton were both command pilots with very distinguished service careers, having logged several thousand hours flying time each. They were assigned to the Pentagon with highly classified assignments and were perfectly familiar with even the most secret foreign and domestic aircraft designs. Neither had seen anything remotely like those objects before, but they indicated
that they had probably witnessed what friends of theirs had observed, “flying saucers.”

Blue Book made their own study and located all delta wing jets, then exclusively flown by the Navy, yet none were in the Green 3 area. They also checked other sources, which had no records of aircraft, balloons, or anything of any kind over Carson Sink at the time.36 Although only one of 22 reports which made it into ATIC that day, and just one of about 100 worldwide sightings for the 24th, the Carson Sink Sighting, case number 1584, is the best of those in the files marked unidentified.

Edward J. Ruppelt version:
Here is a "good" UFO report with an "unknown" conclusion:

On July 24, 1952, two Air Force colonels, flying a B-25, took off from Hamilton Air
Force Base, near San Francisco, for Colorado Springs. The day was clear; not a cloud
in the sky.

The colonels had crossed the Sierra Nevada between Sacramento and Reno and were
flying east at 11,000 feet on "Green 3," the aerial highway. At 3:40 P.M., they were over
the Carson Sink area of Nevada when one of the colonels noticed three objects ahead of
them and a little to the right. The objects looked like three F-86's flying a tight V formation.
If they were F-86's the should have been lower, according to civil air regulations, but on a
clear day some pilots don't watch their altitude too closely.

In a matter of seconds the three aircraft were close enough to the B-25 to be clearly seen.
They were not F-86's. They were three bright silver, delta wing craft with no tails and no
pilot's canopies. The only thing that broke the sharply defined, clean upper surface of the
triangular wing was a definite ridge that ran from the nose to the tail.

In another second the three deltas made a slight left bank and shot by the B-25 at terrific
speed. The colonels estimated that the speed was at least three times that of an F-86.
They got a good look at the three deltas as the unusual craft passed within 400 to 800
years of the B-25.

When they landed at Colorado Springs, the two colonels called the intelligence people
at Air Defense Command Headquarters to make a UFO report. The suggestion was
offered that they might have seen three F-86's. The colonels promptly replied that if the
objects had been F-86's they would have been able to recognize them as such. They
colonels knew what F-86's looked like.

Air Defense Command relayed the report to Project Blue Book. An investigation was
started at once.

Flight Service, which clears all military aircraft flights, was contacted  and asked about
the location of aircraft near the Carson Sink area at 3:40 PM. They had no record of
the presence of aircraft in that area.

Since the colonels had mentioned delta wing aircraft, and both the Air Force and the
Navy had a few of this type, we double-checked. The Navy's delta's were all on the
east coast, at least all of the silver ones were. A few deltas painted the traditional navy
blue were on the west coast, but not near Carson Sink. The Air Force's one delta was
temporarily grounded.

Since balloons once in a while can appear to have an odd shape, all balloon flights were
checked for both standard weather balloons and the big 100'-diameter research balloons.
Nothing was found.

A quick check on the two colonels revealed that both of them were command pilots
and that each had several thousand hours of flying time. They were stationed at the
Pentagon. Their highly classified assignments were such that they would be in a position
to recognize anything that the United States known to be flying anywhere in the world.

Both men had friends who had "seen flying saucers" at some time, but both had openly
voiced their skepticism. Now, from what the colonels  said when they were interviewed
after landing at Colorado Springs, they had changed their opinions.

(Source: Michael David Hall, "UFOs, A Century of Sightings", Page 187 & Captain Edward J. Ruppelt's,  Report on Unidentified Flying Objects, Page 10).