The UFO speeds we see are deceiving. A technology that warps space like a black hole could punch in and out of normal space, appearing to make immediate right-hand turns or travel great distances from its last location. Inside the warped field, there would be no movement or inertia. The fine tuning of bending space is phenomenal for some UAPs and different for UFOs that are triangles compared to the tic tacs.
This kind of navigation is the opposite of propulsion of pushing mass. It is more like pushing space. A partial engagement of space warping would appear to be linear travel. A full punching out of normal space would be like disappearing.

There is testimony that the one and only time the US went to defcon 1 was in response to a UFO - aircraft carrier interaction. When all communication was lost with the US convoy, the worst was feared.