Unidentified Flying Objects – or UFOs – have long seemed the preserve of conspiracy theorists and alien-fearing folk sometimes depicted as the people in tinfoil hats.
But did you know that the United States Air Force once took them so seriously that it had an official programme to investigate sightings called Project Blue Book?
Some might find it surprising too that the US Department of Defense last month opened a new chapter in the investigation into sightings of objects in the skies.
It established the Airborne Object Identification and Management Synchronization Group (AOIMSG), to investigate every report of an airborne object in its airspace, whether identified or unidentified, and it says it will take every report very seriously.
That office was this month renamed the All-domain Anomaly Resolution Office (AARO), which will sit across all of the services, US Army, Navy and Air Force, and will become the central office to collect, investigate and manage reports of Unidentified Aerial Phenomena (UAPs) and other unidentified objects, such as those underwater, around the world.
The US space agency NASA (National Aeronautics and Space Administration) last month also announced that it had commissioned a new study to examine unidentified aerial phenomena (UAPs) to investigate observations of events in the sky that could not be identified as aircraft or known natural phenomena, from a scientific perspective.
In a statement, a spokesperson for NASA said: "Unidentified phenomena in the atmosphere are of interest for both national security and air safety.
"Establishing which events are natural provides a key first step to identifying or mitigating such phenomena, which aligns with one of NASA’s goals to ensure the safety of aircraft."
The space agency cautioned, however, that there was no evidence that UAPs were extra-terrestrial in origin.
Such sightings are no longer referred to as Unidentified Flying Objects (UFOs), however, but instead, Unidentified Aerial Phenomena (UAP) – in other words, anything seen by pilots or others in US airspace that cannot be simply explained and needs further investigation.
What, however, are the beginnings of official US organisations and their concerns over unidentified phenomena?
A look back to the US Air Force programme to log reports of unidentified objects in the sky during the late 1940s to the 1960s reveals how seriously the US military took reports of this kind and the lengths that it went to investigate such sightings.
Watch: UFO expert 'puzzled' by Pentagon's decision to release UFO footage.
What was Project Blue Book?
Project Blue Book was in operation from 1947 to 1969 and was an official US Air Force mission to document and investigate reports of UFOs to determine if they posed a threat to national security, or a risk to pilots, or if they were examples of advancements in hostile states' technology that might have caught America unawares.
Part of the thinking behind the concept was that unexplained events in the skies could be examples of as yet unidentified technological phenomena that may or may not be the work of other countries such as Russia or China, or could even be technology that was beyond human control that represented some kind of incomprehensible potential threat.
In its 22 years of operation, it had collected reports of 12,618 sightings which were all logged, investigated, analysed, and filed.
While investigations into the vast majority of the sightings concluded that they were likely to be misidentifications of natural phenomena, such as clouds, reflections of lights, stars, and debris blowing in the wind, for example, or simply sightings of conventional aircraft mistaken for other phenomena, those working on the project could not explain 701 of the cases and these have remained on file as "unidentified" ever since.
In the 1960s, concerns over the sighting of aerial events that could not be explained led the military to turn to the academic science community with a request to carry out an independent study into the data recorded in Project Blue Book.
The US Air Force sponsored the research which fell to the University of Colorado in 1966, under the direction of physicist Edward U Condon.
Over two years until 1968, the University of Colorado's UFO project, informally known as the Condon Committee after its director, reviewed and reinvestigated the findings in Project Blue Book, with the aim of deciding if any further investigation was needed.
The scientific committee examined hundreds of UFO records from the Blue Book, and other reports made by civilian UFO groups.
However, the research eventually concluded in a final report that the study of UFOs was unlikely to yield any major scientific discoveries and the programme was disbanded and Project Blue Book was terminated the following year in 1969.
Examples of UFO sightings logged in Project Blue Book
With more than 12,000 sightings, there are far too many to mention but, to give an idea of the kind of incidents recorded by Project Blue Book, a few examples give an insight into which reports caught the attention of investigators.
It is difficult to pinpoint exactly when the concept of airborne phenomena, which might have been thought of as unknown advanced technology or even other-worldliness, entered the American national, if not global, psyche in the 1940s.
Perhaps one of the earliest, documented, and most well-known sightings of a UFO came in 1947.
Businessman Kenneth Arnold was reported to have seen a grouping of nine airborne objects travelling at high speed as he flew his small plane near Mount Rainier in Washington, USA.
He reported that the aerial phenomena, which were crescent-shaped, had been travelling at excessively high speeds that he estimated was several thousand miles per hour, and were moving like "saucers skipping on water".
His sighting was reported by a newspaper which mistakenly printed that the phenomena were saucer-shaped – thus inadvertently coining the term 'flying saucers', a term for UFOs that has persisted ever since.
In the months and years following that report, more and more people began to report other sightings of airborne objects, perhaps prompted by the publicity given to Arnold's claims and, by 1947, the US Air Force began to take an interest.
The question was, while many sightings could be put down to simple publicity-seeking or exaggeration, what if some of those sightings had credibility – such as the possibility of hostile nations developing advanced technology, or what if any suggestions of visits by extra-terrestrial lifeforms were true, and what if that posed a threat to national security?
This, in turn, gave birth to Project Blue Book – to document any such sightings and investigate their credibility and some of the following documented sightings give a sample by way of example.
On 13 October 1952, an object said to have resembled planet Jupiter was reportedly spotted heading in an easterly direction over York in Pennsylvania. The object was said to have remained in sight for about 12 seconds, at an altitude of 5,000 to 10,000ft.
On 17 July 1957, a pilot reported seeing a blue light in the air which stayed with his aircraft for about 420 nautical miles. The sighting appeared to be more than just a light as it was picked up as a moving object by the radar of a US air force B-47 bomber plane. The object could not, however, be picked up by ground radar.
Investigations suggested that it could have been a domestic passenger jet, American Airlines flight 655, but questions remained and there are reports of that explanation being logged as inconclusive.
In another sighting listed in the documents of Project Blue Book, on 17 April 1966, Sheriff deputy Dale F Spaur, of Portage County Sheriff's Office in Ravenna, Ohio, reported an intense light coming from a metallic object rising out of a row of trees near where he and a fellow officer were patrolling. They reported that there were no coloured lights but a very bright, silvery radiance.
They followed the light for about 80 miles as it was said to fly about 500ft in the air, slowing down and then going very fast as it went.
The glow was said to be so bright that it blinded the driver of the vehicle. Other witnesses were reported to have seen the object along the route between Ravenna, Ohio, and Conway, Pennsylvania.
Three men from the sheriff's office and two patrol cars followed the object along the route before it disappeared out of view.
Watch: Fast-moving UFO caught on camera by US Navy.
How the Blue Book programme was carried out
The programme was carried out in three phases which included the air force bases closest to the reported sighting taking charge of responsibility for the investigation and, then, if initial identifications could not be found, escalating the report to phase two which included further analysis.
The third phase would include the dissemination of information regarding the reported sightings when all other examinations had failed to provide identification and the unidentified object required further discussion and investigation of the evaluations and statistics from the first two phases.
The US Air Force documented its findings into three groups: identified, insufficient data and, thirdly, unidentified.
What is the current thinking around unidentified objects in the skies?
In June 2022, the United States reopened the concept of investigations into sightings of airborne objects.
The House of Representatives intelligence subcommittee heard from two senior US defence intelligence who told the meeting that the Pentagon was committed to determining the origins of what is now known as 'unidentified aerial phenomena' rather than Unidentified Flying Objects.
While they acknowledged that some sightings were beyond the government's ability to explain, Ronald Moultrie and Scott Bray spoke frankly at the first public American congressional hearing on the subject of unexplained sightings in more than 50 years.
The hearing was held following a government report which had recorded more than 140 cases of unidentified aerial phenomena (UAPs) which had been seen by military pilots since 2004.
A new office to examine such sightings was launched, under the title Airborne Object Identification and Management Group.
However, earlier this month (July), the Pentagon announced that the remit of the group had been expanded and the office renamed as the All-domain Anomaly Resolution Office or AARO.
The office's new remit will not only include looking into the skies and outer space for objects of interest but would also examine objects classed as unidentified submerged in water, or what the US government calls 'transmedium', which is objects that can move across or through multiple environments such as through the Earth's atmosphere but also move underwater or into space.
It comes as the House of Representatives voted to create a new governmental system for reporting UAPs as part of amendments to this year's defence bill and which would also task current and former defence officials to be transparent about such phenomena.