The pilots apparently started picking up these strange objects after radars aboard their Super Hornet warplanes were upgraded to "a more advanced system", and the radar sightings were soon followed by visual detection.

Frequent sightings of enigmatic flying objects capable of performing maneuvers seemingly impossible for terrestrial craft were reported by US naval aviation pilots operating over the country’s eastern seaboard, according to The New York Times.

As the newspaper explains, the flying objects, which showed up "almost daily" from the summer of 2014 to March 2015, were able to reach altitudes of up to 30,000 feet and hit hypersonic speeds despite possessing no visible engines and not leaving exhaust plumes.

"These things would be out there all day", Lt. Ryan Graves, an F/A-18 Super Hornet pilot, said. "Keeping an aircraft in the air requires a significant amount of energy. With the speeds we observed, 12 hours in the air is 11 hours longer than we’d expect".

The encounters apparently started occurring after pilots of the VFA-11 "Red Rippers" squadron stationed at Naval Air Station Oceana in Virginia, had the 1980s-era radars installed aboard their Super Hornets "upgraded to a more advanced system", the newspaper notes, but were initially ignored due to being considered false radar tracks.

Lt. Danny Accoin, who, along with Graves, was part of that squadron, said he interacted with these objects twice, with one such encounter involving a training missile on his jet locking onto the enigmatic bogey which also showed up on his infrared camera.

"I knew I had it, I knew it was not a false hit," he said. But still, "I could not pick it up visually".

Later, however, the pilots started actually seeing these objects which seemed to be able to attain hypersonic speeds and perform sudden stops, as well as to turn around instantaneously, which should be impossible

"Speed doesn’t kill you. Stopping does. Or acceleration", Lt. Graves remarked.

He also observed that while mankind did make "helicopters that can hover" and "aircraft that can fly at 30,000 feet and right at the surface", a vehicle which can perform all these feats "with no jet engine, no exhaust plume" would be something else entirely.

READ MORE: US Navy's New UFO-Detecting System to Keep Sightings Secret From Public − Report

Earlier this month, the Washington Post revealed that new guidelines established by the US Navy will require pilots and other staff to report encounters with unidentified flying objects, though the military apparently does not intend to make this data available to the general public.