While taking scenic photographs in estes park near the hotel we were staying at, i snapped two photographs showing an object in the sky that moved from my right to the left. the photos were taken 4 seconds apart, and the object moved a large distance within that time. it apparently changed direction slightly. interestingly, while taking the photos, i did not notice the object in my camera's view. i only noticed the object after, when i was flipping through the images. i didn't hear any sounds, or feel any vibrations other than the wind blowing. it should be noted that the denver airport is approximately a 1.5 hour drive from where the photos were taken.