Driving west on Colorado Hy 24 near Chipita Park, Colorado. Talking on cell phone when me and my two kids noticed and aircraft to the northwest. My friend on the other end may now think I am crazy. :-) It was Silver and oval, moving extreamly slow. Its slow speed is what got my attention. It was moving much slower than an airplane, especially for its size. We lost view as we drove due to the elevations, but got a 2nd good view ~.5 miles later. It was hard to tell its altitude as this is a very hilly area, but it appeared to be flying low. Its low altitude also made this odd. This is the 1st time I have ever reported a UFO. I saw something I cannot explain. My kids are 13 & 10 and they could not figure out what we were looking at. Should have, but did not, try to get a cell phone picture.