I was in North Denver waiting for the bus after work.Two twinkling objects were seen at two different times within five minutes far above the Western horizon. They were either flying further west or were dropping altitude, but both floated down several degrees in vision while seeming to expand and contract, and then finally they disappeared. I might've thought they were jets if it weren't for the fact that they left no trail of exhaust. They both simply appeared in the sky and dropped down on the vertical plane of vision while changing shape and floating down, kind of like a feather does. The first one disappeared outright, just fading out of the sky. I may have lost sight of the second one only because it flew further west(?) behind a cloud. A few minutes after the sighting, a jet with a short stream was seen flying to where the objects were spotted in the sky. I lost sight of it when it disappeared behind the same cloud as the UFO. The experience intrigued and frightened me.