Bright blue/white light flies silently across evening sky.I was sitting in my backyard swing when I noticed a bright blue/white light flying across the sky from the north. The light appeared to be at low level, I would estimate not higher that 5000 feet. The light flew slowly across the sky in a straight line until it was almost due east of my position then it turned at about a 45 degree heading toward the southeast. There was no sound, which I thought odd because of the low altitude. The object was the same blue/white color as a mercury vapor street lamp with no apparent red or green navigation lights and no strobe. A few minutes after the object had disappeared behind the tree line, a commercial aircraft flew over at an estimated altitude of 30,000 feet and it's engines were clearly audible. I'm a retired aircraft mechanic with 20 years service in the Air Force and I am quite familiar with most of the aircraft that frequent Barksdale AFB and the Shreveport airport. This is a first for me. I don't know what it was.((NUFORC Note: ISS flew over Louisiana at 21:01 hrs. on this date, but the description provided by the witness does not appear to conform to the Space Station. PD))