While on my balcony, I watched flights, some local, some commercial. Thje sky was slightly overcast with high haze, moving west to east. Some stars were visable, including part of the big dipper.I saw a distinct crescent shaped form, moving from east to west. There was no light, eratic movement or change. simply a thin cloud-like "C" shape moving across the sky. Had I not been in a reclining posture, I would not have seen it.The form went by rapidly, but not so fast that I didn't have time to comprehend what was happening and concentrate on the object.Were I to hazard a guess, I would say that a "black" object was moving across the sky and creating a pressure zone ahead of it's path.