Triangle shape with one red light in center flying low, slow, and quiet over wooded, mountainous area.My father came into the house, a bit before 10pm, reporting a strange, triangle-shaped object in the sky. I asked him if it was still there, he said "No," (to my disappointment). I then questioned him. He said it was a dark triangle shape flying much lower than a plane would. It had only one light; a red light in the center of the object. He said that there was only the faintest sound (barely audible), much fainter than what one would expect from an airplane, and especially an object flying so low. He also said that it was moving more slowly than a plane, and was a very smooth, low, & slow glide from the woods behind the house until it went out of his site. The object flew in a straight line until out of sight. The area around the house is very mountainous and wooded. He was very calm and non-chalant, as he believes it was some sort of military test craft. However, I wanted to share this encounter in case it is ever of value.