Gray and white object flying in formation of 12

I saw this formation which I thought was seagulls, but then I noticed a jet flying at an altitude that I estimated to be 20k feet. So, I didn't think it was birds.
The formation consisted of 12 craft. They all moved at the same speed, and in the same direction. The tail section looked like a v, and was gray in color. The front section, looked like a square, with the sides shaved off. It was white in color. I know I am not doing a very good job of explaining what I saw, but please bare with me. As I watched the formation, it took a turn to the north and disappeared. Then it appeared a few minutes later to the left of where it had disappeared. It continued to repeat the formation and the disappearing for about seven minutes, then it went away. I drew a picture of what I saw if you want it.