I never believed in it, and I don't think anyone else did either:)
These were perceptual errors, fantasies, and so on.
At worst, they were elves or some kind of similar creatures:D:D
By the way, there was an interesting study of UFO descriptions; it was compared with descriptions of encounters with elves and other magical beings in folklore and medieval texts, and... they were amazed. The similarity was striking - to the point that in medieval texts, before the appearance of evil forces, horses traveling on the road would stop, become frightened, and absolutely refuse to move further, while in UFO descriptions, cars would break down and fail when they approached.
So, if there were any such phenomena, I am more inclined to believe that people saw spirits, elves, or evil forces, which, due to their mindset, saw as aliens (in this high-tech style).