Chanute AFB, IllinoisMarch 1961

On the evening of March 9, 1961, five military members at Chanute Air Force Base in Illinois reported seeing an unusual bright object in the sky. The witnesses described it as round and white, comparing its size to a basketball or watermelon. The object appeared near the gatehouse areas around dusk and moved through the sky in various ways, at times pulling up gradually, banking, and descending behind buildings before fading from view. Individual observation times ranged from about two to five minutes.

The Air Force investigation looked closely at weather conditions and air traffic that evening. The sky was overcast with broken clouds, light snow showers, and good visibility. Weather records indicated a warm, dry layer of air between 3,500 and 12,000 feet, which can bend light and distort how objects appear in the sky. The investigator also noted that Venus was the brightest star visible that night at the angle and direction where witnesses saw the object.

The real clue came from flight records. A T-33 training jet was conducting a practice approach with its landing light on while a C-47 transport plane was circling in a holding pattern in the exact area where witnesses spotted the object. The investigator concluded that the combination of these aircraft, low fast-moving clouds, stars shining through gaps in the overcast, and the distorting effect of the warm air layer all likely contributed to the sighting. He also noted that witnesses had discussed what they saw before officially reporting it, which may have influenced their accounts.

The Air Force evaluation marked this case as unknown, though the investigator's detailed analysis pointed toward aircraft and atmospheric conditions as the probable explanation. The complete case file, containing ten pages of documents held by the National Archives, is reproduced below.