Madrid, Spain, July 1955July 1955

Two physicians vacationing in Madrid, Spain saw a dark circular object cross the evening sky on July 14, 1955. The men were sitting on the patio of the Castellana Hilton Hotel just after sunset when they noticed what appeared at first to be a large bird. As they watched, the object became clearly outlined against the bright sky as a perfect circle, appearing about one-third the size of the moon. It moved steadily from northwest to northeast in what they estimated took about one and a half to two minutes, traveling over the city and then accelerating to what seemed like supersonic speed as it moved eastward and disappeared over the horizon.

The witnesses described the object as solid and perfectly round, black at first and later appearing chocolate-colored as it passed overhead. They estimated it was between 100 and 200 feet in diameter, though their size estimates shifted somewhat as they reflected on the difficulty of judging such distances against an open sky. The evening was clear and calm with no wind. One of the observers, who had a private pilot's license and flew frequently, attempted to photograph the object with a 35-millimeter camera. The witnesses ruled out several conventional explanations for what they saw. They were confident it was not a bird, aircraft, weather balloon, satellite, or optical illusion.

The Air Force investigator who interviewed the men months later rated them as reliable observers. The men both held doctoral degrees and seemed confident in their descriptions of speed, distance, and altitude. One of the witnesses noted that the object moved far too slowly over Madrid to be a conventional aircraft, and this inconsistency troubled both observers. The Air Force concluded in its report that the most likely explanation was an aircraft, possibly a jet flying at low altitude, which would appear dark and could accelerate to high speed. However, the preparing officer acknowledged that the sighting came from only one observation point and that definite conclusions could not be made.

The full case file is reproduced below as held by the National Archives and consists of 26 pages.