More than ten United States (US) scientists have gone missing or been killed in recent years, with fears that American adversaries are behind the incidents. Most of the scientists had links to sensitive American nuclear and aerospace research.

Both the Federal Bureau of Investigation and the Republican-led House Oversight Committee, the main investigate committee of the House of Representatives, the lower house of the American parliament, have said they are launching investigations into the disappearances.

President Donald Trump called the incidents “pretty serious stuff” while James Comer, the top Republican on the House Oversight Committee, was quoted as saying: “It does appear that there’s a high possibility that something sinister is taking place here. It's very unlikely that this is a coincidence. Congress is very concerned about this. Our committee is making this one of our priorities now because we view this as a national security threat."

Eric Burlison, another Republican member of the committee, said: “I would not be surprised if our adversaries, China, Russia, Iran, or any other adversary, saw an opportunity to take out some of our nation’s top scientists.”

There have also been claims that some of the scientists who have been killed or have gone missing were involved in research into Unidentified Aerial Phenomenon (UAPs), which had previously been called Unidentified Flying Objects (UFOs).

The most high-profile person on the list of missing people is Major-General William Neil McCasland, who worked on classified space weapons research and worked at Wright-Patterson Air Force Base in Ohio. In conspiracy circles, the base has long been alleged to be involved in research into UAPs and to contain the remains of debris of an extraterrestrial craft, which was purported to have crashed at Roswell in New Mexico in 1947.

The 68-year-old McCasland went missing in February, leaving his house and not giving any indication where he was going.

Other scientists who have disappeared include Monica Reza, an aerospace engineer, who worked for a rocket design and engine company in California. She went missing in 2025 after going on a hike. She also did work for the National Aeronautics and Space Administration (NASA), the American space agency.

Amy Eskridge, who had cofounded the Institute for Exotic Science in Alabama, died from what authorities ruled was suicide in 2022. However, acquaintances of hers subsequently came forward and said that she had explicitly told them she was not suicidal.

Carl Grillmair, a 67-year-old scientist who had done research on exoplanets (planets outside of our solar system) and had worked with NASA, was shot dead outside his home in Los Angeles in February.

A former Air Force intelligence officer, Matthew Sullivan, who was in his late 30s, died of undisclosed causes in 2024 (some reports have said it was believed to be suicide), shortly before he was due to act as a key witness for congressional investigators looking into UAPs. He also worked at the same air force base in Ohio where McCasland had worked.

However, family members and friends of the missing or deceased scientists have come forward to dismiss speculation that the deaths are connected. Other critics have said that unrelated deaths have been linked with no evidence by conspiracy theorists for content or clicks on the internet.

While it remains to be seen whether there is something sinister behind the deaths and disappearances, the US has a long history of conspiracy theorists believing that there is a shadowy cabal (sometimes linked to the US government, sometimes not) behind much of what happens in America and the world. While it is more than likely that the deaths are unrelated, and true that humans often see links where they do not exist, a full investigation by the authorities should be welcomed to get to the bottom of the matter.