A video has surfaced of Navy F/A-18 fighter jets encountering an unidentified aircraft off the East Coast in 2015, media reports say.
Fighter jet surveillance video shows it encountered the object roughly four nautical miles away over the ocean.
A Pentagon spokesperson Monday would say only the Defense Department did not release the video.
In December, the Pentagon confirmed to this news outlet and others it investigated service members claims of reported UFO sightings decades after Project Blue Book headquartered at Wright-Patterson Air Force Base concluded.
In the 1960s, Project Blue Book was an Air Force program that investigated worldwide reports of unidentified flying objects. The investigations, which concluded in 1969, found no threats to national security or evidence of extraterrestrial vehicles, the Air Force has said.
The Advanced Aviation Threat Identification Program inside the Pentagon ended around 2012, according to the Defense Department.
The $22 million program ran between 2007 to 2012, The New York Times reported late last year. At the time, the Pentagon released two videos of an encounter between Navy F/A-18s and unidentified aircraft off the West Coast in 2004.
To The Stars Academy of Arts and Science, a private scientific research organization, released the latest declassified Defense Department video of the 2015 incident, media reports say.
Christopher Mellon, a former deputy assistant secretary of defense for intelligence in two prior presidential administrations, recently called on the Pentagon to take the reports seriously and investigate the cause of the sightings.
“If the origin of these aircraft is a mystery, so is the paralysis of the U.S. government in the face of such evidence,” he wrote in a Washington Post Op-Ed column Friday.