By Mike Wendling, BBC News
The Pentagon is seen from the air in Washington, DC, on March 2, 2022. Photo: AFP / Brendan Smialowski
A spike in UFO sightings in the 1960s was likely caused by tests of advanced US spy planes and space technology, a Pentagon report has concluded.
Officials also said there was "no evidence" that the US government had encountered alien life.
Most sightings of UFOs were ordinary objects from Earth, according to the report submitted to Congress on Friday.
But Pentagon officials accepted that their research won't quell popular beliefs about alien guests.
"The proliferation of television programmes, books, movies, and the vast amount of internet and social media content centred on UAP-related topics most likely has influenced the public conversation on this topic, and reinforced these beliefs within some sections of the population," it said.
The report is part of a broad public attempt by the US government to examine UFOs - or as officials call them, "unidentified anomalous phenomena" (UAP).
The effort has included public meetings with NASA officials and hearings in Congress.
Issued by the Pentagon's All-domain Anomaly Resolution Office (AARO), the report noted that public opinion has probably been swayed by pop culture.
A "particularly persistent narrative", the researchers said, is that the government has recovered spacecraft and alien remains and has conspired to keep its alien research activities secret.
A Pentagon spokesperson said that officials had approached the report in an open-minded way, but had simply found no evidence of extra-terrestrial visitors.
"All investigative efforts, at all levels of classification, concluded that most sightings were ordinary objects and phenomena and the result of misidentification," Major General Pat Ryder told reporters.
According to a 2021 Gallup poll, just over 40 percent of Americans think alien spacecraft have visited Earth, a number that increased from 33 percent in just two years.
The AARO examined archives and classified files and reviewed all official government investigations dating back to 1945.
The researchers hunted down rumours about alien spacecraft and found, for instance, that an alleged 1961 leaked memo about UFOs was inauthentic, and that an "alien spacecraft" sample collected by a UAP investigating organisation was not made of an otherworldly material but instead was made mostly of magnesium, zinc and bismuth.
The AARO has promised to issue a further report examining more recent sightings and rumours.
- This story was first published by the BBC.