After more than four decades in the cockpit, retired pilot Chris Crowther has seen just about everything the skies can offer.

Over a 42-year career, he logged an extraordinary 22,000 flying hours on routes around the globe.

But one incident has puzzled with him for nearly half a century.

It happened in 1978, as Crowther, who lives near Wroxham, Norfolk, was piloting a light aircraft on approach to Norwich Airport.

In a split second, he says, something crossed his path – something he still cannot explain.

Decades later, the memory remains as vivid as ever, raising a question that continues to intrigue aviation professionals and the public alike: what exactly are we seeing in our skies?

"We were coming across The Wash at 7,500ft (2,300m) when Eastern Radar [a joint civilian/military air traffic control centre that existed until 1988] called up and said, 'We've got unidentified traffic, opposite direction, fast moving... height unknown,'" Crowther recalls.

"We looked up and in that split second, something went past our starboard wing tip, so fast it was very hard to define, but I still have the image in my mind of what looked like a dozen dark objects, perhaps the size of a football... something like that, that went winging right past our wing tip... and then they were gone."

Crowther did not report this sighting, but his account is far from unique. In recent years, sightings of claimed unidentified flying objects (UFOs) – now more commonly referred to as unidentified anomalous phenomena (UAPs) – have shifted from the fringes of public curiosity into mainstream discussion.

Nowhere has this shift been more pronounced than in the United States, where the government has released a tranche of declassified documents and military pilots, intelligence officials, and whistleblowers have come forward under oath to share their experiences.

Their testimony has described encounters with objects capable of manoeuvres far beyond known human technology, alongside claims of secretive crash retrieval programmes.

While scepticism remains, the growing official acknowledgement has helped fuel global debate and renewed interest in the phenomenon.

Film director Steven Spielberg has returned to the subject, which he first explored in 1977's Close Encounters of the Third Kind, with his new movie Disclosure Day.

It imagines a world on the brink of the revelation of proof that non-human intelligence exists and has been hidden in plain sight.

Unlike the US, the UK currently lacks a formal, centralised system for recording or investigating UFO sightings.

The Ministry of Defence (MoD) once operated a dedicated UFO desk, assessing reports for potential threats to national security.

However, it was shut down in 2009, largely due to defence budget cuts.

Since then, there has been no official mechanism for the public – or even trained observers, such as pilots – to report unusual sightings.

For some, that represents a worrying blind spot.

David Jon, a former National Crime Agency officer based in Leigh-on-Sea, Essex, has made it his mission to address what he sees as a growing gap in national security and scientific understanding.

His agency has 32 UFO cases from across the world on its books, two of which are still open.

He says he and his team use police-style techniques in their investigations, and that while most sightings can be explained, about 20% cannot.

He believes the UK risks falling behind in understanding potential threats – or opportunities – linked to UAPs and is calling for closer collaboration with international partners.

"I want the government to take this subject seriously and put some money behind it," he says.

"People are now more empowered... people have a 4K camera in their pockets these days, so we are capturing a lot more evidence but there's nowhere to report them to.

"It doesn't mean our airspace is not experiencing the same things [as the US]; indeed, I'd argue we've had a lot more incidences here in the UK that need proper investigation."

While misidentified aircraft, atmospheric phenomena or even advanced military technology account for many sightings, others remain stubbornly unexplained.

Over a series of nights, US Air Force personnel at twin bases in Suffolk reported seeing strange lights in the forest, along with what some described as a landed craft of unknown origin.

The incident prompted official investigations and has since become a cornerstone of UFO research in the UK.

Pope spent years reviewing reports and interviewing witnesses, including those connected to Rendlesham.

Although he often emphasised that most sightings had conventional explanations, he acknowledged that a small percentage remained unexplained.

Pope wrote extensively on the subject of UFOs and, diagnosed with cancer earlier this year, continued to speak publicly.

He spoke to the BBC shortly before his death in April.

"This wasn't lights in the sky, this was a landing; British and American witnesses, multiple military witnesses," he said of the Rendlesham Forest incident.

"This is a defence and national security issue... People use the phrase 'drone' very loosely these days but there is no getting away from the fact that military bases have been directly overflown by these things, and it's not unreasonable for the British people to want some answers."

Despite these accounts, the official government position remains cautious.

The MoD maintains that no reported sightings of extraterrestrial intelligence, UFOs, or UAPs have ever indicated a direct military threat to the United Kingdom.

That stance offers reassurance but not necessarily answers.

An MoD spokeswoman said she was not aware of any point within the government for reporting such sightings, but added: "If the public are concerned about use of the airspace, they could contact the CAA (Civil Aviation Authority)."

A CAA spokesman said: "To our knowledge, there is no active monitoring of this taking place in the UK and the CAA has never been involved in any such activity.

"A lot of the 'unidentified flying objects' we see reported are unmanned aircraft systems (drones).

"There are also Airprox reports which cover reported near misses or objects close to aircraft to further encourage air safety."

Prof Chris French, emeritus professor at Goldsmith's College, London, is a UFO sceptic.

"The vast majority of sightings don't have any kind of national security implications and also don't have any kind of relevance to the idea of ET (extraterrestrial) invasions," he says.

He says there are research bodies to which people can report sightings, he sees no need for government involvement.

"As a scientist, as a psychologist who's interested in these types of phenomena, the more data the better, as far as I'm concerned," he says.

"But I can see that from the point of view of the government, when resources are tight... they are probably not going to fund any kind of organisation to do this."

For pilots like Crowther, and researchers like Jon, the question is not just whether these phenomena pose a threat, but whether enough is being done to understand them at all.

With no official reporting structure, they fear many sightings risk going unrecorded, their details lost to time.

Crowther would welcome more openness on the subject.

"I think if not, people's imaginations run wild and I think we would all like to know exactly what is going on," he says.

As interest in UAPs continues to grow internationally, pressure may yet build on the UK government to revisit its approach.

In the meantime, incidents like the one Crowther says he experienced remain unexplained.

And for those who say they have witnessed them, the mystery is far from over.

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