This is a two-hour UK TV programme by aerospace journalist Nick Cook, who decided to step outside his comfort zone and take a critical look at the case for unidentified flying objects (UFOs) and the possible explanations for the phenomenon.
The story begins in WW2 with the frequent reporting by RAF bomber crews on night raids over Germany of "foo fighters"; bright lights appearing to move around them. These have never been clearly explained, beyond the fact that very tired and frightened men in a state of permanent stress may be prone to hallucinations which may be "infectious"; if one says he saw something, others may too. Another possible explanation lies in secret Nazi projects such as those conducted in the Wenceslas Mine in the Sudeten Mountains, as reported after the war by a German officer who was based there. As well as vague reports of a "bell" reputedly connected with antigravity research, there is the massive above-ground structure of the "flytrap" which still exists today; a large reinforced-concrete circular framework, apparently with provision for a massive electric power input, for which there is still no explanation.
The focus then switches to Roswell in New Mexico in 1947, with perhaps the most famous UFO story of all; the wreckage of some artificial object of which there are various conflicting reports, ranging from a weather balloon to an alien spacecraft complete with aliens. However, this was only one of many UFO reports from this area, most of which can probably be attributed to the unusual atmospheric conditions which create illusions such as lenticular clouds. Cook interviews several witnesses with conflicting points of view and examines what was going on at the time at the nearby White Sands airbase. Here some 200 German scientists had been based in the years after WW2 as a result of Operation Paperclip, the effort to recruit as many scientists involved in advanced research as possible. At that time the USA was engaged in developing a wide variety of experimental aircraft (including the saucer-shaped Vought XF5U "Flying Flapjack") but the most likely explanation for the Roswell incident was the secret Skyhook project to send huge unmanned photographic reconnaissance balloons over the USSR, which regularly drifted over the Roswell area. Most significantly, Cook obtained evidence that the UFO stories were deliberately encouraged by the CIA as a disinformation scheme to distract Soviet attention from such recce projects (involving planes as well as balloons). This may account for the fact that the USAAF/USAF kept changing its story over the wreckage, and for the existence of one official report which stated that the UFOs may well be alien spacecraft.
One series of sightings for which there is still no adequate explanation, however, concerns the moving formations of lights in the sky widely observed over Washington in 1952. Such was the public concern that astronomer J Allen Hynek was tasked with looking into the question (I recall reading his book on Project Blue Book decades ago). He was able to dismiss the vast majority of sightings as misperceptions but acknowledged that there was no adequate explanation for a small percentage of them. Furthermore, he was only able to examine civilian reports: the potentially much more valuable ones from military pilots were excluded.
The 1960s saw a new development: the growth of "close encounters of the third kind", in which figures were reported walking next to a landed UFO. The most striking report came in 1964 from a police officer called Zamora, who was patrolling in the area of the White Sands base. After considering alternative ideas, Cook identifies the most likely explanation as a secret USAF project based on a development of the unsuccessful Canadian Avro Avrocar "flying saucer", to which the USAF had bought the rights.
There was a great increase in UFO sightings in the UK in the late 1960s, possibly related to a secret US deployment of the SR-71 strategic reconnaissance plane (which may also have been responsible for many UFO sightings around the Nellis USAF base; the notorious "Area 51"). Cook then looks at the series of cases of animal mutilation in the area of Los Alamos in 1976-86 which have been attributed to alien experiments, but he considers more likely to have been a covert US testing and monitoring programme.
The Soviet Union also carried out an investigation into military UFO reports from 1977 to 1990, attributing many of them to missile launches, but concluded that the evidence was inconclusive and that some were unexplained.
Finally comes the period of "alien abductions", which goes back to the 1950s but became an epidemic in the 1980s and 1990s with no fewer than two million Americans claiming to have been abducted. Cook attributes this to a "need to believe", with many of the characteristics of a religion.
In conclusion, UFO sightings can be grouped into various categories. As Hynek identified in the 1950s, the vast majority are a result of misperception of ordinary phenomena: clouds, astronomical objects or routine man-made ones such as aircraft, spacecraft and balloons (the recent craze for flying illuminated "Chinese lanterns" has caused another surge in UFO reports). For nearly all of those which cannot be accounted for in this way, the most likely explanation is that of military "black projects"; it is significant that the CIA encouraged the UFO hypothesis as a way of covering up such activities. The epidemic of alien abduction reports seems most likely to have been the result of a kind of mass hysteria, strongly emotional and quasi-religious.
This still leaves a very small percentage of reports which cannot be explained in any of these ways and remain genuine mysteries. However, it is worth bearing in mind that the U of UFO stands for "unidentified" - which simply means that at the moment we do not have enough information to identify the cause of the sightings. It is a pity that the "alien spacecraft hypothesis" enthusiasts have adopted UFOs since this makes scientists - and even serious journalists - reluctant to consider the issue for fear of losing professional credibility. All credit to Cook for analysing this intriguing subject objectively.