[cesna311]

The answer is simple. I give you a clue : why can't we see any god, angel , seraphim or elohim with all our surveillances devices ? And where are chimeras from popular beliefs, as ghosts ? UFO, like religion in another era/place, is a fun fantasy, sometime emerging spontaneously in people brain, sometime used as a a political instrument by states and/or influential leader. So, the best device for seeing UFO is not a surveillance device, but human ignorance and stupidity.