Whether aliens have visited Earth is still up for debate. Whether we're the aliens—either from the past or the future—remains to be settled. What cannot be denied is that flying saucers are real, and they've been real for more than half a century.
Since the 1940s, Cold War adversaries were racing to construct spacecraft and bizarre aircraft that may or may not have triggered many of the waves of UFO sightings that rocked the planet beginning in World War II. People have been reporting odd ships in the sky since the beginning of history, but by the 1940s people also had cameras.