Project Blue Book Case #190. On July 31, 1948, witnesses in Indianapolis, Indiana, observed a circular object with well-defined edges moving through the sky. This early case came during a critical period in the Air Force's investigation of the UFO phenomenon — just weeks before the Mantell incident investigation concluded and as Project Sign's investigators at Wright-Patterson AFB were actively debating whether the objects could be interplanetary.
Indianapolis occupied a central position in the nation's postwar aviation network, with Weir Cook Airport (now Indianapolis International) serving as a major civilian hub and several military facilities in the surrounding region. The summer of 1948 had produced several alarming cases for Project Sign, including the Chiles-Whitted encounter over Alabama on July 24 — just one week before this Indianapolis sighting — in which two experienced airline pilots reported a cigar-shaped craft with illuminated windows passing their DC-3 at close range.
The Indianapolis object was described as clearly circular in shape, with sharp edges that distinguished it from the fuzzy appearance of astronomical objects or atmospheric phenomena. It moved at a steady pace across the sky without the turbulence-induced wobble of lighter-than-air craft.
Project Sign investigators took this case seriously, as it fit the pattern of structured, daylight-disc observations that formed the core of what the Sign team called the "best evidence" for unconventional craft. The case was classified "Unknown" and contributed to the Sign team's controversial "Estimate of the Situation" — a classified report that concluded the objects were likely extraterrestrial, which was rejected and ordered destroyed by Air Force Chief of Staff Hoyt Vandenberg.