From the book, given any two lines non intersecting lines in 3 space, any two planes each contains one of the lines can always make parallel to each other ( the two planes are parallel). The way the book described is that given two lines, you can produce two vectors V1 and V2, each parallel to one of the lines. Then by cross product V1 X V2, you get the normal vector N. The vector N is also the normal vector for both planes. Therefore the two planes are parallel. Do you have a more convincing way to proof the two planes that contain the two individual non intersecting lines can be made parallel?