I was driving to the post office when out of no where there is a small but bright flash in the clear blue sky around 2000ft away and above me and a that's where the object instantaneously appears. Flying mostly horizontal and a slight bit downward, it has a small white trail behind it and after 1-2 seconds it flashed again and it was gone. The object and the trail as well. As if it were never there. I am pretty sure other drivers on the road with me have to have seen it as well. The biggest thing I noticed was how shiny it was, and it really caught my attention immediately for the few seconds before it disappeared. I did notice a plane flying off in the distance but I live in Denver and see commercial jets and planes as well as military planes pretty often. And this WAS NOT anything like I've ever seen before.