Two people seen this. we worked at a prison. i worked a housing unit as unit supervisor. the other was a perimeter patrol officer. i don't remember the actual dates. and other than the incident i didn't think much of it until watching the history channel which i do alot. i seen a drawing of what i thought to be the same thing i seen,so here it is. i was working a unit on i would say on the back side of the prison when a mobil unit called into central control and reported an aircraft hovering over the tree's. the outside supervisor was not able to come at that time. so my shift supervisor called me to go out the back of my unit and report. this is a maximum security prison so all aircraft reports are very serious to us.I stepped out of my unit i would say 2 to 250 yards to my right was an aircraft hovering a tree top height. no lights no sound. the top of the tree's was not being disturbed. i reported to my shift oic that there was an aircraft and it was making no sound just hovering. looks like a airplane and no noticeable markings no lights. it hovered maybe 3 mins then backed away from the institution turning to its left as it did. a report was written and turned into shift oic. however it was boomerang shape,like the stealth fighter had two white circles oddly larger than what airplane engine's look like where the engine's would be. it made no sound did not disturb not of it's surrounding. no lights at all. 75 miles we have airport. 45 miles we have airbase. really didn't think ufo. however i still don't know what kind of aircraft it was. me an that other officer still talk about that some times even tho i no longer work there. i was there 15 years. and feed back on how many of these type sightings?