Ruppelt's account:

About 11:00A.M. on May 24, 1954, an RB-29 equipped with some new aerial cameras took off from Wright Field, one of the two airfields that make up Wright-Patterson AFB, and headed toward the Air Force's photographic test range in Indiana. At exactly twelve noon they were at 16,000 feet, flying west, about 15 miles northwest of Dayton. A major, a photo officer, was in the nose seat of the '29. All of the gun sights and the bombsight in the nose had been taken out, so it was like sitting in a large picture window--except you just can't get this kind of a view anyplace else. The major was enjoying it. He was leaning forward, looking down, when he saw an extremely bright circular-shaped object under and a little behind the airplane. It was so bright that it seemed to have a mirror finish. He couldn't tell how far below him it was but he was sure that it wasn't any higher than 6,000 feet above the ground, and it was traveling fast, faster than the B-29. It took only about six seconds to cross a section of land, which meant that it was going about 600 miles an hour.

The major called the crew and told them about the UFO, but neither the pilot nor the copilot could see it because it was now directly under the B-29. The pilot was just in the process of telling him that he was crazy when one of the scanners in an aft blister called in; he and the other scanner could also see the UFO.

Being a photo ship, the RB-29 had cameras--loaded cameras--so the logical thing to do would be to take a picture, but during a UFO sighting logic sometimes gets shoved into the background. In this case, however, it didn't, and the major reached down, punched the button on the intervalometer, and the big vertical camera in the aft section of the airplane clicked off a photo before the UFO sped away.

The photo showed a circular-shaped blob of light exactly as the major had described it to the RB-29 crew. It didn't show any details of the UFO because the UFO was too bright; it was completely overexposed on the negative. The circular shape wasn't sharp either; it had fuzzy edges, but this could have been due to two things: its extreme brightness, or the fact that it was high, close to the RB-29, and out of focus. There was no way of telling exactly how high it was but if it were at 6,000 feet, as the major estimated, it would have been about 125 feet in diameter.

Working with people from the photo lab at Wright-Patterson, Captain Hardin from Project Blue Book carried out one of the most complete investigations in UFO history. They checked aircraft flights, rephotographed the area from high and low altitude to see if they could pick up something on the ground that could have been reflecting light, and made a minute ground search of the area. They found absolutely nothing that could explain the round blob of light, and the incident went down as an unknown.

Like all good "Unknown" UFO reports, there are as many opinions as to what the bright blob of light could have been as there are people who've seen the photo. "Some kind of light phenomenon" is the frequent opinion of those who don't believe. They point out that there is no shadow of any kind of a circular object showing on the ground--no shadow, nothing "solid." But if you care to take the time you can show that if the object, assuming that this is what it was, was above 4,000 feet the shadow would fall out of the picture.

Then all you get is a blank look from the light phenomenon theorists.

One disc, about 150 feet across, was observed by military witnesses at a military facility for over three minutes.

Google map of this location.