A stirng of brilliant white lights on a craft

It was a totally clear/cloudless day. I witnessed a string of extremely bright white lights glowing high in the sky to the NE/92117 moving very slowly. The lights were not normal plane/helicopter/etc. lights. They were brilliant white. As I watched for several minutes, it came closer yet remained at a high altitude. That was when I clearly saw its shape of a rectangle or large square, silver, shiny, no wings, a single bright white light in the center front, and a string of the brilliant glowing incredible white separate lights all across the back section from end to end. There was no sound as it moved very slowly to the W. I saw and heard 3-4 private small planes go across the sky at much lower altitude, passing under the craft above them. I wondered what it must look like to those pilots, assuming they would look high above them. I watched at least 15 minutes until the craft was so far W towards the ocean that I lost sight of it. When it actually went overhead where I was/92111, I could see the string of separate lights all across the back end of the rectangle or large square, and the single light in the center front. Only the string of lights glowed brilliantly and could easily have been seen by anyone looking up. They caught your eye because of their brilliance. The craft kept moving the entire time at an extremely slow speed. It made me feel as if it were observing. I kept looking for other people to watch the amazing sight but none were around. Even though the craft was at a high altitude, it must have been huge to be able to see the string of lights on the back end glowing so brightly in the blue sky. I'll never forget it.