Wing-shaped or boomerang-shaped craft at high altitude directly overhead.While sitting on the patio with friends, shortly after sunset I looked directly overhead to view the sun shining on the high, wispy clouds. At the same moment, I saw what at first appeared to be a fast-moving jet moving from NNW to SSE. Because of my location, I could only view about as much of the sky as the equivalent of twice the width of my hand held at arm's length. The object crossed this section of the sky in less than two seconds (possibly as quickly as one second), only long enough for me to barely open my mouth to draw attention to the others sitting with me, but not long enough for me to utter a word. What surprised me about the object was that it was very dark compared to other jets in the air that evening (dark grey) and the way the "wings" met at a right angle, giving the appearance of a carpenter's square flying through the air. There was no fuselage visible. I thought it might be a very large, very fast jet flying at very high altitude or a smaller, slower jet at lower altitude. I observed other jets crossing the sky within the following quarter-hour and, even though some were quite some distance away (i.e. viewed at 45% from the horizon or less), I could clearly make out their fuselages in all cases, they were much lighter in colour than what I had observed earlier, their wings did not have the distinctive right-angled proportions or even width from fuselage to tip, and they travelled at much slower apparent speeds. There was no sound from the object (not necessarily surprising if it were in fact a very high aircraft), although I could hear most of the other aircraft I observed that night, even the high, distant ones. Anyway, it made me curious, and I've been closely watching a lot of aircraft for the past few days and nothing I've seen in the air even closely resembles what flew over on Sunday night. The object's flight path struck me as rather strange, as most commercial aircraft fly either more-or-less on east-west lines in this part of the country or northeast to southwest if they're overseas flights. I've never seen anything flying on so nearly a north-south axis (although this might be a good route for commercial flights from Russia or military craft returning from the far north).