UFO sightings are a reflection of Zeitgeist
The UFO phenomenon, when experienced and reported, is tantamount to an account of the trend and thought of an era, its zeitgeist.
Reports in ancient times, as listed by the Vallee/Aubeck book, Wonders in the Sky, or represented by passages in the Mahabharata, The Hebrew Bible, or other early human texts, can be read or seen as indicative of the patina of human thought and emotion for the period being recorded, mostly rendered with a religious or mythical overlay.
The lacuna of sightings in the Dark Ages or early Medieval era show the mental abyss of the time(s).
With the Renaissance and turmoil (The Church of Rome’s descent) of the Middle Ages is reflected, as I’ve previously noted, in such famous woodcuts as the Nuremberg and Basel.
The ensuing Age of Enlightenment allowed mankind to dwell on human thought, so a need for UFOs in that period was nil, and a lack of sightings show that, just as the Romantic era of art and music indicate that mankind was inclined to harbor thoughts of a creative or transcendental kind, obviating a need for an external phenomenon to be necessary.
The 1890’s Airship wave, like music and art, show the mental construct of the era as steeped in a yen to modernity, which was stoked by the Industrial Revolution.
The modern era of UFO and flying saucer sightings/accounts came about from the subliminal distress of the World War II aftermath and Cold War, as Jung explains in his flying saucer book: Flying Saucers, A Modern Myth in Things Seen in the Skies.
The hodgepodge of weird sightings with odd entities reported in Europe in the 1950s tells us that those countries were more distressed than we in the States, although there is a remnant of similar accounts (Flatwoods and Hopkinsville) here during the time-frame.
As the Cold War dissipated, so did UFO sightings, now reminiscent of the foggy human mindset for our era: humankind and society not striving for some connection to things greater than either.
UFOs, today, are without, hallucinatory elements which are prominent in the 1950s or the need to understand life and nature that was a feature of early cultures.
We have settled into a bland substrate of existence and UFOs have virtually disappeared from the superficial zeitgeist that now exists.
The veneer of current human stupidity or obsession with technology has removed, pretty much, the need for a mythical phenomenon.
Thus UFOs are gone from the general human psyche and this era’s zeitgeist is cleansed of such folly.