Driving north on Greenspring Avenue, I noted this low flying white color sun-reflecting object flying above the treeline faster than a helicopter. It looked like two inverted circular cake pans with a protruding lip. It traveled in my visibility for about 30 seconds and disappeared. There were other cars on the road at the time, but no one stopped to watch. Interesting to note, I first spotted it over the area where an old Nike missile base used to be. It appeared to be no bigger than the front seating area of a helicopter. What brought it to my attention was its reflective quality.When I checked on the Internet to see if anyone else saw it, I saw an article about a 2/14 siting in Baltimore's Inner Harbor with a picture. The shape of that UFO matched what I saw.