Half-circle ufo seen from the back yard in Arkansas.

I don't remember the exact day, but it was a big day for me, being my first day to live with my dad and stepmother.  My sister and I were playing in the back yard, when we both noticed what I first thought was a parachute.  It was a half-circle, flat on bottom, and just white.  I though it was strange, though, that there was no man hanging underneath it.  There was no sound at all, and it just seemed to hover in one spot.
I pointed up to it, and my sister and I watched it for a few seconds....then it either vanished in a blink, or sped away at a speed too fast to see, but it was just suddenly GONE.  We looked at each other for a second then we ran into the house to tell our parents what we just saw.
My sister today has no memory of that day, but I remember it like it was yesterday.  I can see it clearly in my mind as clearly as if I just saw it today.
Witness indicates that the date of the event is approximate.  PD