Unlike any known aircraft, these objects have been sighted overcoming the earth’s gravity with no visible means of propulsion. They also lack any flight surfaces, such as wings. In the Nimitz incident, witnesses describe the crafts as tubular, shaped like a Tic Tac candy.

The objects may accelerate or change direction so quickly that no human pilot could survive the g-forces—they would be crushed. In the Nimitz incident, radar operators say they tracked one of the UFOs as it dropped from the sky at more than 30 times the speed of sound. Black Aces squadron commander David Fravor, the Nimitz-based fighter pilot who was sent to intercept one of the objects, likened its rapid side-to-side movements, later captured on infrared video, to that of a ping-pong ball. Radar operators on the USS Princeton, part of the Nimitz carrier group, tracked the object accelerating from a standing position to traveling 60 miles in a minute—an astounding 3,600 miles an hour. According to manufacturer Boeing, the F/A 18 Super Hornet fighter jet typically currently reaches a maximum speed of Mach 1.6, or about 1,200 miles an hour.

If an aircraft travels faster than the speed of sound, it typically leaves "signatures," like vapor trails and sonic booms. Many UFO accounts note the lack of such evidence.

Even when objects are observed, getting a clear and detailed view of them—either through pilot sightings, radar or other means—remains difficult. Witnesses generally only see the glow or haze around them.

Some UAP have been seen moving easily in and between different environments, such as space, the earth’s atmosphere and even water. In the Nimitz incident, witnesses described a UFO hovering over a churning "disturbance" just under the ocean's otherwise calm surface, leading to speculation that another craft had entered the water. USS Princeton radar operator Gary Vorhees later confirmed from a Navy sonar operator in the area that day that a craft was moving faster than 70 knots, roughly two times the speed of nuclear subs.

No one has yet gotten close to crafts that display these traits, so their origins are still unknown. Are they a super-top-secret U.S. defense project? Do they hail from Russia? China? Or from even further afield? The only thing we do know is that their capabilities exceed any technologies currently in the U.S. arsenal.