Shimrod - They don't need to be brightly lit. It's just that they're a hell of a lot easier to see in the night sky when they are brightly lit, that's all. The ones that aren't usually go by without being noticed by anyone. However, I have personally witnessed UFOs at night that were either brightly lit...or barely lit at all. Then you have the daytime UFOs, and they can have a variety of appearances, some having visible lights on them, some not. Most often, they seem to have a silvery appearance when seen in daylight...like polished metal.