SIGHTING REPORT UFO sighting at Belchertown, MA

It was triangular, larger than a large jet (unless it was landing), and there were no lights-flashing or otherwise-which I could see. It was very dark, I could only make out its shape as it blocked the stars.

It was moving too slowly, I think, to be an airplane or a jet, and while it didn't move quickly its movements were too controlled. It seemed to move straight for a time, and then move sideways without turning (although that last part may have been a trick of the night sky).

I live near a military airbase (nothing secret at all) and there are frequently such large planes as C5-A's taking off and landing at the time of year when I saw this object. I didn't pay it much notice at the time, which is why I didn't follow it for very long (it was certainly visible for longer than the time I watched it). In retrospect, it seemed odd that it made no sound, the C5-A's make a noise like thunder that occasionally rattles the nearby homes. Also, unless it was taking off or landing somewhere nearby and therefore at a low altitude, the object was significantly larger than a C5-A.