I saw something big and pitch black fly between my building and the building across the street that was completely silent.

I was sitting in my chair facing the window, the lights in my room were out and a big thing with no lights and almost no sound flew between my building and the building across the street. I was kind of far away from the window so the passing object was only in sight for maybe half a second. It was ovular with what looked like a vertical stabilizer on its rear end, which makes me believe it was a propellor plane or a particularly long helicopter. However, it made almost no sound and had no identifying lights, unlike any other helicopter I had seen. My roommate and I will often hear helicopters and open the curtains to look at them long before we can actually see them, so I know that they aren't usually this quiet. I ran down the hallway to try to see it out another window but I couldn't. In the seconds after I saw it, I was expecting an explosion due to how low flying the thing was.