Dark, aerodynamic shaped object near Frisco, CO.I was finishing up a photo shoot of a vacation rental in Breckenridge, CO, and was traveling back to Frisco, CO. I pulled over near a hospital to photograph a mountain.I use a method called bracketing to photograph my subjects and I took six exposures of the mountain and the third exposure included an aircraft of some kind that seemed to be miles away. The other exposures did not contain this aircraft even though they were taken within seconds of the exposure in question.I am a 20 year AF vet and I currently work as a contractor to the Air Force.