Chicago, Illinois, [ILLEGIBLE]Date unknown

On the early morning of September 2, 1952, the radar control tower at Chicago's Midway Airport detected dozens of unidentified targets on their scopes. Starting shortly after midnight, controllers observed what they estimated to be around forty objects moving across their radar screens. These targets resembled aircraft on radar, but their behavior was unusual, and their exact identity remained a mystery.

The radar operators tracked the objects traveling at an estimated average speed of around 175 miles per hour at altitudes near 2,000 feet. The targets appeared most clearly on the six to thirteen mile radar range. Some appeared to fly in formation or follow local aircraft traffic patterns. In one notable instance, two targets were observed flying wing-to-wing alongside an incoming civilian flight from the east toward the airfield boundary, before the right target broke away to the right and the left target turned to the left. The operators reported good azimuth and elevation readings using their Giffillan radar equipment.

Air Defense was notified at 0020 hours (12:20 a.m.), and two F-86 Sabre jet fighters were dispatched from the base at 0535 hours (5:35 a.m.) to investigate. The jets flew multiple passes over the area between 800 and 8,600 feet altitude, directly through the locations where radar had indicated targets. Despite being vectored toward several of the radar blips, both pilots reported no visual sightings of any objects. By 0702 hours (7:02 a.m.), most unidentified targets had vanished from the radar scope. A similar but less intense radar event occurred early on September 3. Weather conditions at the time included broken clouds at 10,000 feet, fifteen-mile visibility, and northwest winds of twelve to thirteen knots.

The Civil Aeronautics Administration tower chief, Robert Zeigler, reported to the press that the radar reflections were likely caused by some unusual atmospheric condition, though the exact nature remained unexplained. The full case file is reproduced below as held by the National Archives, comprising 12 pages of documents from microfilm roll 15.