Three points of light, flying formation, demonstrating control of inertia and momentum.

I was on the roof of our home (most houses in Athens at that time had flat roofs)with my Dad observing the stars with a small telescope. My Dad noticed what appeared to be a spacecraft in low orbit, illuminated by the sun which had just set. I saw it, then we both saw a second spacecraft (both pinpoints of light) "below" it, or in formation, abeam it and maybe 100 miles to the side of the other. We watched these for a few minutes, tracking our heads in the direction of travel, when we noticed with our peripheral vison a third light approaching from the opposite, and slightly below, other direction. They abruptly stopped when they met to form a perfect equilateral triangle. Then they paused, and moved off in a third direction. A short time later a family friend screeched to halt in front of our house, asked if we saw it and repeated our observation adding that he had had a yard full of people who also saw it.