Happened to notice this object slowing moving westbound as I was traveling eastbound on the 91 freeway toward Riverside.

The object moved very slow at the estimation of height of a helicopter's flight pattern. It was about the size of a large bus, cylindrical in shape, with a black glass type front end and silver metal type body with additional black side panels. There were what appeared to be 2-3 fin type appendages in the rear of it. I didn't pull over or stop my car because of traffic concerns. I literally passed under it as it moved toward the 15 freeway. Didn't appear to look like a blimp of any kind. No lights or noise from it. In the far distance toward the east was a commercial airline, but nothing close to it.