An extreemly close sighting of a black/dark grey "minivan" shaped craft.

My friend((Name deleted))and I were sitting on the back patio of my parents condo on a golf course.  It was almost midnight.  Out of the corner of my eye I saw something coming diagonally over us from behind.  I alerted ((Name deleted)), and we both got a good long look.  It was approximately the shape of a minivan, and about twice as big.  It was dark grey or black in color, and we approximated that it was between 40 and 60 feet above us, and traveling away from between 30 and 60 miles per hour.  It was virtually silent, except for a slight hum, possibly displaced air. It had no markings that we could see.  The most amazing thing was how it moved, completely steady.  It never sped up, slowed down or wavered in it's course, it was as if it was on a track.  It was so unusual seeing something as large as it was traveling so smoothly, quietly, and slowly in the air without wings.  It was truly defying gravity. It passed over our heads, over the golf course, and then into the desert heading east. Shawn and I have always been bothered by the fact that the description of our sighting does not match any others that we have heard or read. Why was it moving so slow, why did it not have any lights, why was it not shaped like most "UFO's" we hear about. I wish I knew!!!