Project 10073 Record Card and Air Intelligence Information Report IR-01-57

On 7 February 1957, between 1053Z and 1232Z, the 685th Aircraft Control and Warning Squadron at Las Cruces Air Force Station, New Mexico, detected 54 unidentified radar blips. These targets were observed traveling from the north toward the station at speeds ranging from 60 to 160 knots and at altitudes between 6,000 and 14,000 feet. The targets disappeared approximately three miles out and failed to reappear north of the station. Initial sightings were also reported by the 666th Aircraft Control and Warning Squadron at Roswell, New Mexico, though they lacked sufficient movement data to establish a track. Fighter-interceptor aircraft from the 15th Fighter-Interceptor Squadron in Tucson and the 93rd Fighter-Interceptor Squadron in Albuquerque were scrambled, but no unusual sightings were reported. One encounter involved four targets that were lost in ground clutter, followed by a fleeting radar contact with 13 targets approximately 100 miles north of El Paso, Texas. No further contacts were made by search aircraft, and the area was patrolled for approximately 40 minutes with no results. Consultation between the Air Defense Command Weather Detachment at the 34th Air Division and the Air Defense Command concluded that weather conditions in the area were conducive to a temperature inversion, which could cause the observed radar effects. The controller on duty at the time of the incident also attributed the targets to temperature inversions. An alternative possibility was raised regarding Strategic Air Command (SAC) aircraft, specifically KC-97, B-47, and B-36 types, which were in the air at the time. It was suggested that due to terrain-induced 'dead spots' around the 685th AC&W station, these aircraft could have flown over the site, turned, and flown down the Rio Grande River to El Paso without being detected again after an initial fade. The final conclusion of the headquarters was that the number and speed of the targets, combined with the lack of visual confirmation and definitive radar contact by interceptor aircraft, supported the assessment of anomalous propagation due to a temperature inversion.