Discs have been seen to make 90-degree turns instantly, and in some rare cases, instantly reverse their direction of travel. When accelerating to speeds estimated to be supersonic, no shock wave seems to be generated and no sonic boom is heard. Some maneuvers accomplished by UFOs would place extraordinary stress on the airframe if flying like conventional aircraft. Coming in contact with the surrounding atmosphere at high rates of acceleration would challenge the structural integrity of the vehicle, would induce enormous drag and heat the skin of the craft to glowing temperatures, but perhaps the UFO does not come into direct contact with the atmosphere, but actually repels the atmospheric boundary layer surrounding its form. This would account for how they can move quickly without encountering air resistance and thermal stress.
Structural integrity is a major factor in aircraft design and construction.
No production airplane leaves the ground before undergoing extensive analysis of how it will fly, the stresses it will tolerate and its maximum safe capability. Every airplane is subject to structural stress. Stress acts on an airplane whether on the ground or in flight. Stress is defined as a load applied to a unit area of material. Stress produces a deflection or deformation in the material called strain.