flying triangle in fulton county illinois (1991)

this took place off rt. 100 near ST.David,IL. In the summer of 1991.  I was leaving my girlfriends house, she was living with her grandparents at the time.  I was getting into my car & saw 3 very bright lights right above the tree tops in the front yard.  This house is located in rural ST.David along a busy road "rt. 100".. My girlfriends grandpa was looking out the window & so was she, we all saw this object.  It was a very clear night, many stars.  We coud make the shape out to be a black triangle, it wasnt a very large craft, mabe 20-40 feet.  It made NO noise at all, & it moved like a balloon(very slow).. We watched it move away & it climbed altittude till it dissapeared into the sky, went up into the stars where we couldnt tell its lights from the star lights.
Date is approximate.  PD