I was stading on my front porch looking easterly when I first spotted a large closed horseshoe shaped object heading east from about one o'clock in the sky. The object was clearly defined, and I could see details of the structure and interior lines although the object seemed to be translucent with a white outline and sky blue interior. This may have been because of the altitude of the craft. It appeared as the size of a basketball at about 100' or less. I estimate that it was atleast 400' long and wide (approx. equal). I suspect that it was 2-5 miles in altitude. Any farther would have made it unbelievably hugh. Each side of the craft (port and starboard) was glowing a rosey pink as if heat was being generated there. There was another smaller craft tailing the larger, and it followed at a constant distance of an estimated 500'. It was dificult to see details of the smaller because of the white and gray smokey trail it left behind. It appeared to be bullet shaped with a shiny, metalic nose and a reflective glassy material (cockpit?) behind that. The rest of the second object was obscured by the smoke. The viewed part seemed to be approx 40' long and 15-20' wide. They travelled west to east along the Arizona/Mexico border. It took from 1.5-2 seconds to cover an estimated distance (to the horizon) of 25 miles.