Lots of things can fool us into thinking we've seen evidence of extraterrestrials. What is a UFO to one pair of eyes is readily identifiable to another. Here are a few stories of mine.
Just after dark one summer night, I spotted an ink-black triangular shape hovering about 30 degrees above the horizon. It seemed motionless for awhile, then it quickly moved forward with a jerky, pausing motion. Then it stopped for awhile and actually began moving backwards in the same lurching fashion. It never moved up or down; always forward or backward. I was only 12 years old and thought for sure this was an alien spacecraft. I was really getting excited about it when I felt a rush of air from something whizzing by my head. The triangle shape was still there. It wasn't that that had buzzed me. I ducked and thought "They must have spotted me watching them and they're sending tiny spy thingies toward me!" Then I had the idea that "they" might actually be flying those little spy thingies and "they" were teeny little creatures! After all, whoever said super-intelligent aliens had to be any bigger than a man's thumb? Maybe we could squash them if we ever caught them! There it was again! That whizzing thing next to my head. I ducked again and ran away. I was really freaked out about this UFO experience ... until the next day when I saw a kite - that's right, nothing but a lousy kite - flying close to the same spot I had seen the UFO. It might not have been the same kite, but I knew right away that what I had seen really was a kite. It was just too dark to identify it and it never crossed my mind somebody would be flying a kite at night. What had buzzed my head then? A bat, I'm guessing. It was summer and I had seen bats overhead from time to time just after dark. It was probably just a coincidence that one whizzed by my head while I was watching this "UFO."
Then there was the time I saw a meteor that had broken up as it careened through the sky and it looked exactly like an extremely fast-flying cigar-shaped craft with a bright "cockpit" light at the front and several "windows" following the main light. Of course, the "windows" were just trailing fragments of the meteor. This also could have been misidentifed as a large craft with some smaller crafts following it, since a couple of times the smaller fragments seemed to move slightly closer to and farther away from the central trail of the meteor, giving the impression they were being "steered" to stay in the group. It really did fool me at first, and I thought it might be a plane crashing, but it was moving way too fast and the smaller lights moved around a bit. Plus it all fizzled out in the sky within a few seconds, the smaller bits burning up first.
On another cloudless night, I was lying on my back looking up into the sky for no reason. Just by chance, I focused on a section of sky that contained a tiny dot of light that I thought was a faint star. But as I stared up at that area for several minutes, I got the impression that the one dot had slowly creeped a bit compared to the surrounding stars. After a few more minutes, I was sure of it. The dot had shifted position relative to the other objects. I figured it couldn't be a conventional aircraft. It was at least 20 times too slow-moving to be a plane unless a plane was somehow flying at several hundred miles altitude. I also chuckled at the thought that if this was a sighting of some extraterrestrial craft, it was about as boring as one could be. Then the obvious dawned on me. I was probably looking at a communications satellite that was positioned above the Earth and the motion it seemed to show was only that of the Earth rotating, so the satellite looked like it was moving at "mid-day shadow speed" among the fixed stars.
On still another occasion, I saw a blue-green fireball shoot silently across half the night sky at a low trajectory and disappear somewhere on the horizon, only to "rise" again and fly off into the sky. This was probably a large meteor that gave the illusion of landing and rising when it neared the horizon, owing to the greater refraction of light nearer the horizon than directly above.