Strange object, gliding over my town.

On August 18th, about 6PM, I happened to look out my 2nd story apartment window, which faces east.  I saw what I believed at first to be a large bird, gliding smoothly as large birds often do.  
But as I looked closer, I saw this was a "W" shaped object with depth, almost like a paper airplane viewed from the rear, but I could see the full side as well.  
The object was all black.  It was maybe three quarters of a mile away, and only a few hundred feet altitude.  I would estimate it was about the size of a small private airplane.  I would estimate it was going 20-30 MPH, not fast at all.  Unfortunately, I did not get much of a look, because it glided down behind some trees which obstructed my view.  I watched for several more minutes, but never saw it again.
I drew this picture on my computer.  It is close to the shape, except this object was completely black.
 http://img.photobucket.com/albums/v403/Winman/Object%20in%20sky%202_zpsur8gtmjg.png