I saw a silver object flying SE to NE. No Aircraft running lights.

I was watching the sky for aircraft as I often do. I was a TSO for the TSA, and I like to count the number of aircraft I can see at any given Time. I observed a silver oval shaped craft moving quickly from the SE of my position going NE. I am very familiar with the size and shape of most commercial and military Aircraft. This was not any of them. It was moving after dusk with no running lights or strobes. It was at an altitude of approximately 1000 feet. As I watched it for several minutes it simply disappeared. The light didn't fad, it was gone. The object looked to be larger than a commercial aircraft. I judged it to be about a mile or so away and appeared to be the size of a golf ball.