At the end of the 1940s, UFO sightings increased steadily, particularly in the USA. In 1952, the US Air Force intelligence service and the CIA started “Project Blue Book". The goal was a systematic study to collect and analyze UFO sightings. The end of the project was decided in 1969 and all works stopped by the end of January 1970. With Project Blue Book the CIA wanted to analyze the UFO-phenomenon and its impact on the American population. Without empirical data on how people would react to an encounter with extraterrestrials or their crafts, national security was seen as being at risk. Since the secret service had come into possession of documents about a revolutionary German propulsion concept in World War II, the CIA commissioned the Bell Aircraft Company with the design of an earthly, bell-shaped aircraft for reconnaissance and observation (RO = Reconnaissance and Observation) as a top-secret black project. The revolutionary engine concept required such an unusual shape of the aircraft that whoever would see it in the sky identified it as a real, alien UFO. Beginning in 1959, the work of a small team. The CIA made sure, that non of the team members had any family connections and had never appeared in publications. Those engineers worked and lived at a secret base in the middle of nowhere. Their work led to the first terrestrial UFO, the Bell YRO-10 "Liberty Bell". The Y stood for test vehicle. Two prototype aircraft were built. The name "Liberty Bell" was chosen as nickname by the CIA because of its shape, which reminded remotely of the Liberty Bell in Philadelphia. The rotationally symmetrical bell shape was cut by a cockpit module with enough space for one pilot. In case of an imminent crash this module was supposed to be blasted off to cover up any tracks and distract from the earthly roots of the aircraft.
