It was a nice sunny day and I was going over to my best friends house just after 10AM. And as I was walking out to my car I happened to look up to the west and saw what I assumed was a jetliner, but it was going really slow. I kept looking up at it thinking that plane is going to stall out and crash cause I didn't hear anything, it was completely silent. It was headed directly toward DIA as so many planes do like it was making it's final approach. But then I was thinking to myself, "that doesn't look right". I had aircraft identification in Civil Air Patrol and couldn't see any wings or engines. But I thought maybe I'm seeing it at a bad angle and if I keep watching it I'll see a wing or engine. The whole time thinking it's going too slow. Then I noticed this thing doesn't even have a tail, there was no tail or stabilizer(rudder). I kept walking to my car and looking up at it every few seconds. I got in my car and as the car was warming up, I watched it more intently and noticed the windows running the length of the fuselage were bigger than a passenger plane has. They were more rectangler and bigger than planes have. I hadn't noticed it sooner because there was a dark blue thick stripe running down the length of the middle of the fuselage. Above and below the blue stripe the rest of the fuselage was metallic like a lot of planes. That's why I didn't really notice at first this thing didn't have wings or engines because of the blue stripe. As I started driving I turned the corner of my street going very slow so I could keep watching it, looking away for just a second or two (didn't want to hit one of the parked cars on the street). All of a sudden I looked back up and it was gone. So I pulled over and looked around everywhere, it was gone! There were no trees or obstructions of any kind. I thought maybe I was wrong about it and kept looking for it or a plumb of smoke and fire from a plane crash. I never did see it or any fire or smoke. As slow as it was going I would have seen it if it was a plane going in that direction.