There's also bubbles of swamp gas, birds, weird atmospheric optical phenomena, miscalibrated radars, and hoaxes.

I'm not hugely interested in figuring out which one of a million different, mundane explanations is responsible for any particular UFO sighting. There's a never-ending stream of those sightings, all of them very low-quality, and they never amount to anything interesting. Maybe some spy wonk somewhere three stories underneath the Pentagon has looking at them as his OKR, but I don't get paid for it!