I know this might seem trite in light of your description above, but there is a difference between being skeptical of unlikely things and being a closed minded bigot. I guess it comes down to your comment about knowing "the truth." It appears that you must consider yourself more enlightened than everyone else, since you know "the Truth" but refuse to share it with us. Pray tell, how do you know the difference between someone seeing strange lights in the sky and someone seeing a spaceship from another world? Because it seems to me that all the proof we have of the latter is a bunch of grainy photos of strange lights in the sky, which kind of leads me back to option 1 as the default for these things.
It's also not fair to site pilots, astronauts, doctors or anyone else who sees strange lights in the sky and say they are any better than anyone else at this stuff. How many astronomers do we hear of seeing UFOs? How many sightings also have indisputable radar echos to go along with them? Otherwise it's just people seeing strange lights in the sky that could be anything, so the number of them seeing these things isn't relevant, nor is their profession unless they are professional people who look at the sky for a living, and even they might not know the source of some mysterious light if they saw one. Still, it's a far cry from "lots of people see a weird light" to "lots of people see alien spaceship".
As for alternatives to what these particular lights might be, I have no idea, but I'll bet there are million mundane explanations that come before "alien spaceship buzzing earthlings." You don't have to make up exotic explanations for these things either. In the past these lights have turned out to be flares dropped by planes, various types of balloons reflecting or carrying lights, flocks of geese reflecting light off their bellies, aircraft flying at an odd angles to the observer, meteor showers, and on and on and on. So, if you want to prove it's aliens, you have a long way to go.
That's your first mistake. I don't claim to know the truth about UFOs. That you conclude otherwise speaks more about your own mindset than mine. It seems to me that you're the one who claims to know the truth based more on what you don't know than on what you do.
In the past these lights have turned out to be flares dropped by planes, various types of balloons reflecting or carrying lights, flocks of geese reflecting light off their bellies, aircraft flying at an odd angles to the observer, meteor showers, and on and on and on.
You forgot swamp gas. No doubt the upside-down pie plate with a glowing underside and what looked like windows in the side that my aviation-industry-connected husband and his son, along with several neighbors, saw above their neighborhood in the early 70s (near an air force base, by the way) was a flair or a flock of geese. What idiots my husband, his son, and his neighbors must have been for not being able to discern the difference, which you surely would have! Either that, or he is a liar in very good company, including many extremely well-qualified aviation and law enforcement professionals.