Close Encounters of the Third Kind - And the #1 Sign Your Spaceship Is Flying Too Low...
Near the end of the film, when the really really BIG spacecraft is coming into the landing area, the ship's enormous black shadow is shown engulfing all the onlookers below.
Now, the luminous source that was lighting the area at the time was a set of big stadium lights placed around the landing pad. However, the spaceship was flying ABOVE these stadium lights, so no shadow should have been cast.