He and other officials spoke on condition of anonymity as they were not authorized to speak publicly about the secret results of the report.

Russia has invested heavily in hypersonic, believing the technology gives it an opportunity to evade American missile defense technology. China has also developed hypersonic weapons and included them in military parades. If the phenomena were Chinese or Russian aircraft, officials said, it would suggest that the two powers’s hypersonic research had far outstripped American military development.

Marine pilots were often unsettled by the sightings. During an encounter between summer 2014 and March 2015, strange objects appeared almost every day – one of them like a top moving against the wind – high in the sky over the east coast. Navy pilots reported to their supervisors that the objects had no visible engine or infrared plumes, but that they could reach 30,000 feet and hypersonic speeds.

Lt. Ryan Graves, an F / A-18 Super Hornet pilot who served 10 years in the Navy, told the New York Times in an interview, “These things would be out there all day.” At the speeds he and other pilots observed, he said, “12 hours in the air is 11 hours longer than we would expect.”

In late 2014, a Super Hornet pilot had a near-collision with one of the objects and an official accident report was filed. Some of the incidents were videotaped, including one captured by an airplane camera in early 2015, showing an object zooming across the ocean waves as pilots ask what they are seeing.

The Department of Defense has been collecting such reports for more than 13 years as part of an opaque, little-known Advanced Aerospace Threat Identification Program within the Pentagon. The program analyzed radar data, video footage, and reports from Navy pilots and senior officers.

The program began in 2007 and was funded largely at the request of Harry Reid, the Nevada Democrat who was the Senate majority leader at the time. It officially closed in 2012 when the money ran out, according to the Pentagon. But after publishing a 2017 New York Times article about the program and criticizing program officials for not reporting reports of aerial phenomena, the Pentagon restarted the program last summer as the Unidentified Aerial Phenomena Task Force.