3 flat, large white lights in delta pattern, no sound, flying at tree-top level at 35-40 mph

As I exited my car and was walking toward my front door, I glanced up to the sky and was surprised to see three large circles of white light in a triangular pattern sailing tree-top level over some trees in my side yard.  I walked out into the yard for a better view and didn't feel fearful since "it" was flying away from me in a southwest/northeast direction at approximately 35-40 mph.  The light was a flat type with no projection.  Perhaps the strangest thing I noticed, in addition to the whole senario, was the absence of any sound.  I didn't see any structure around the lights but they were in a triangular/delta pattern.  I watched it until it disappeared, then went into the house and called my boyfriend who lived 1-2 miles away in the direction that the ufo was traveling.  He looked out but saw nothing.  For a day or two, I watched the newspaper for any other reported sightings, but saw none.  All I can say is, I know what I saw and I don't care if anybody believes me or not.
Date is approximate.  PD