Whatever unidentified foreign objects have been spotted in the sky will remain a mystery, at least for now. According to the AP, “Investigators have found no evidence the sightings are linked to aliens — but can’t deny a link either. Two officials briefed on the report due to Congress later this month say the U.S. government cannot give a definitive explanation of aerial phenomena spotted by military pilots.”

U.S. Navy pilots have reported seeing mysterious objects in the sky numerous times over the years. The New York Times writes:

The report determines that a vast majority of more than 120 incidents over the past two decades did not originate from any American military or other advanced U.S. government technology, the officials said. That determination would appear to eliminate the possibility that Navy pilots who reported seeing unexplained aircraft might have encountered programs the government meant to keep secret.

But this doesn’t mean the mission to identify the UFOs is over.

The Washington Post adds:

One senior defense official, who spoke on the condition of anonymity because the report’s details have not been made public, said one possible explanation is that the aircraft belong to adversarial nations harnessing unknown technology.

The Pentagon is increasingly focused on competing with Russia and China, which are making strides in advanced technology, including hypersonic and directed energy.

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