Observed a round boomerang shaped object gliding through the sky

Three people sitting in a backyard in Brooklyn observed a round boomerang shaped object flying across the sky.  It was at first thought to be a parachute but did not have a person or weight attached- and instead of gliding like a parachute, it was advancing steadily through the sky as a plane would.  There was no visible engine nor trails, and it was completely silent.  It appeared to be moving south towards the north at a airplane like speed, and disappeared out of view behind the buildings.