A Flash of light from inside the cab of the truck.

My father and I were driving one night going to a friends house.  We were passing through a wooded area.  All of the sudden the entire cab of the truck lit up with a pale blue light from inside the cab.  It was bright.  I could see the entire inside of the truck.  I looked outside but did not see any light coming from the outside.  I asked dad what was it.  He said he had no idea.  That happened when I was 11 years old.  We would bring it up every once in a while and we still don't know what it was.  The sky was clear that night.
Date is approximate.  PD