Project 10073 Record Card — Thurmon, Colorado, 11 May 1955

On May 11, 1955, at 0106Z, a commercial pilot flying for American Air Lines reported observing an unidentified aircraft while at an altitude of 20,000 feet over the Sangre de Cristo range in Colorado. The pilot noted that the object displayed no vapor trails or other distinguishing characteristics that would allow for a positive identification of the aircraft type. The sighting was recorded on a Project 10073 record card. The official evaluation concluded that the object was an aircraft, though it remained unrecognized by the witness. The report explicitly states that the immediate identification of the object as an unrecognized aircraft precluded further investigation into the sighting as a potential UFO. The investigating authorities noted that the pilot was experienced, but suggested that the combination of scattered cloud conditions at all altitudes and limited visibility prevented a more precise identification. Consequently, no further investigation was authorized. The documentation includes a record card, an index card, and an information report detailing the flight parameters, noting a true airspeed of 315 knots and a southeast course. The report also mentions a follow-up communication with a Lieutenant Mc Fetridge.