Until the age of 4 I would see lightening people dart quickly about outdoors. Adults couldn't see them. About 8 years later I developed migraine with the light flashes so it may be explained that way.

In my early 20's I saw a gigantic tuble of light cross the sky in just a few seconds.
In my mid 20's I and others saw globes of light pass through the brick wall of my home.
In my forties I saw and heard large craft pass overhead with an electic throbbing hum that was intimidating enough to stay put and NOT wave my arms yelling "Here I am!".

Whether there are living entities that either appear strange in our dimensionality or intellighet radiant energy is an interesting question but I would not personally call them ghosts.