My friend and I live on the western slope of Colorado, Rifle, as we were sitting outside we noticed 2 bright lights flying in unison at the exact same speed. Suddenly one of them dissappeared and right after the other did. As we watched they would dim and slowly come back, then dissapear over and over. During all this I was on the phone with my brother 30 miles away in Glenwood Springs and as I was freaking out over the phone he decided to check out the sky as well. Amazingly enough he and his roommate saw the same lights flying over head. In this 30 mile radius is rough terrain and high mountains, there is no way it could have been airplanes seen in both these locations.