Two high altitude, high speed lights half hour apart, no sound, no blinking, yellowish color

We were camping May 23rd through May 26th 2008 just south of Priest Lake, Idaho.  At around 10pm, one of our friends noticed a bright light moving rapidly from southeast to northwest.  There was no sound at all.  The light was not blinking and there was only one light.  It was about 3 – 4mm at arms length with a slight yellowish ness to it.  I thought it looked a little oval in shape.  It was much too big to be a satellite (I don’t think they have lights anyway - ?).  Its path was straight as an arrow and its speed was constant.  My 16 year old son thought he could see it wavering very slightly.  If it was an airplane or a helicopter there would be definite sound and blinking lights.  As it reached the horizon there were some clouds silhouetted in the sky, I could see the light go through or above them, it was hard to tell.  Either way, there were clouds between us and the light.  So I estimated its altitude as being quite high.
At about 10:20pm, one of our party noticed a bright flash to the south, about the size of three or four average size stars combined.  No one else saw it at that time.  We don’t know if the lights had anything to do with each other or not.
At around 10:30pm, we saw another light exactly like the first.  Size, brightness, speed, direction, apparent altitude, everything was just like the first, except this one was a little more to the South.  This light also disappeared over the horizon to the Northwest.
Some time after, about 11:15 or so, we were all glancing up at the stars.  I then saw a flash as well, which was about the size of three or four stars combined.  It looked almost like a camera flash.  It came from the same Southerly direction as the first flash at about 30 degrees in the sky.  Once again we don’t know if the two incidents are connected in any way.
As a footnote, two of our car batteries died and had to get jump started.  One died just as it arrived at the campsite and one the morning after we arrived.  Both had died before we saw the lights.