Some of these "objects" may be projections. The "dot" at the end of a laser pointer defies physics too if you were only to think of it as a physical object of approximately the same size.

I think there are a few tricks military R&D came up with to have people chasing phantoms, but they don't always fill in the public if they see some use outside of a testing range.

For example you might have a beam emitter on the ground that's tuned to around half the frequency needed to excite atmospheric gases. Then you use two of them that are synchronized and phase shifted, and where the two beams overlap - it effectively starts to excite the gas in that zone into ionization. It starts emitting light, and will also reflect radar.

With something like that, you can have other people chasing that around just like you would your pet with a laser pointer.

Not saying all UFO's are that, but some of the current tech developments make this kind of electronic warfare stuff quite possible since it does have some uses. (Other than creating false returns to have somebody chase, it can be used to reflect narrow beam communications or for stuff like over-the-horizon RADAR.)