Project 10073 Record Card — Cheyenne, Wyoming, 16 July 1957

On July 16, 1957, at 11:57 MST, a civilian observer in Cheyenne, Wyoming, reported an unusual aerial phenomenon involving vapor trails. The observation lasted approximately five minutes. The witness described a very faint and narrow vapor trail that formed a 180-degree arc in about 12 seconds. No aircraft or object was visible at the head of the trail. The report notes that an unusual pattern developed, consisting of vapor trails forming at right angles to the main arc, creating a cross-like appearance that was wider than the primary trail. Approximately 30 seconds later, a second, separate trail was observed moving from west to east in a straight line. The sky conditions at the time were reported as having scattered broken clouds at 8,000 and 15,000 feet. The observation was documented on a Project 10073 record card and a formal report was submitted to the Air Defence Command at Ent Air Force Base in Colorado Springs. The official conclusion reached by the evaluating authorities was that the phenomenon was caused by 'Other Contrails.' The comments section of the record card explicitly states that there was nothing unusual about the sighting, noting that such trails are frequently observed in association with aircraft, even when the aircraft itself remains invisible to the observer due to high altitude.