Chicago, IllinoisJune 1952

On June 11, 1952, a Chicago resident watched two dark blue, globular objects with grey centers move across the sky above northwest Chicago. The observer was standing outdoors about seven miles east of O'Hare International Airport when he noticed the objects passing overhead in hazy outline. They moved from southwest to northeast at an estimated speed of 500 miles per hour, traveling at roughly 6,000 feet altitude. The second object appeared to take the lead, passing the first object to its left before both disappeared. The entire sighting lasted between 30 and 45 seconds.

The observer did not report his sighting to the Air Force until after a "Flying Saucer" newspaper story appeared in Chicago. However, his written notes recorded at the time matched the weather forecast for that exact period, and he appeared to have experience judging aircraft altitudes and speeds. He emphasized that the objects were definitely not conventional aircraft. The weather at the time was scattered clouds at 6,000 feet, a broken ceiling at 12,000 feet, and overcast conditions at 25,000 feet, with fifteen miles of visibility.

The Air Force investigation found no known atmospheric condition or activity that could account for the sighting. No photographs were taken, and no aircraft traffic in the area was identified. In a later review from 1968, an Air Force officer noted that the piball balloon theory seemed unlikely because such a balloon would have had to be very close to create the apparent motion described, and it could hardly have flown directly against a surface wind of 25 miles per hour. He concluded that proper interrogation by competent investigators at the time might have cleared up the situation.

The Air Force evaluation for this case was unidentified. The full case file, comprising 29 pages as held by the National Archives, is reproduced below.