UFOs observed by air crews and from the Earth's surface are known to behave extremely mysteriously in flight. They can approach the aircraft at high speed from the side and, having instantly extinguished the lateral approach speed to zero, freeze next to the aircraft flying at high speed, flying in a completely different course - parallel to the aircraft. Then they can also instantly move away to the side, sharply changing their course of the same name with the aircraft to orthogonal. Such maneuverability of UFOs is completely inexplicable by modern physics.

So, any aircraft has mass, and mass, in accordance with the laws of physics, has Inertia. Then it always takes Time to overcome this Inertia («Time»  in its utilitarian sense, see Secrets of the Time Machine). In addition, such changes in course and speed are incompatible with the life of the crew operating the apparatus. These living creatures must be crushed when performing these operations! A mystery arises - how does a massive UFO instantly change its flight course and speed? Maybe aliens have different physics? Maybe in their physics there are other laws?

No, not the other one. No, not others. It's just that the creators of UFOs know Nature better than modern physicists Earthlings. So, in modern physics it is not known what mass is. This is confirmed by the modern existence of many concepts of mass: gravitational mass, inertial mass, relativistic mass, rest mass, mass of motion. The beauty!?? Mass is a fundamental concept in physics, but there is no concept!

In modern physics, the deep essence of Inertia is also unknown. It is believed that the cause of Inertia lies in the depths of the Universe, which does not allow revealing its essence (see About E. Mach's principle).

Thus, mass - no one knows what, Inertia - no one knows what! That's the reason for the UFO mystery. Then, to reveal this secret, we will use the Unified Theory of Nature. It establishes both the essence of mass and the essence of Inertia (see Essence of mass - ether vortices and Inertia - a consequence of the elasticity of the ether). The Unified Theory also reveals the deep essence of Gravity (see Gravity is not attraction). One of the results of revealing the deep essence of these fundamental concepts of physics is the developed design of the inertialess antigravity spacecraft Umbrella. This device allows you to instantly gain maximum speed without the manifestation of Inertia (see Spacecraft Umbrella). Accordingly, no harm is done to the crew either. Due to the exclusion of Inertia, this apparatus can also change course along any broken line and at any angle, including 180 degrees.

Here is the solution to the mystery of the incredible maneuverability of UFOs. They work on the basis of the deep essence of the phenomena of Nature (see Concepts of the Unified Theory of Nature).