A novel was open in his lap, but he had for a while been distracted by planes taking off and landing, by passengers walking tarmac to or from parked planes, and by hand-pushed or motor-driven vehicles taking gasoline or air or food or luggage to or from these planes. He had been watching all this without noticing the people.  He had somehow gotten focused on the straight or bent or serpentine patterns it was taking for all these movements to flow without people or things colliding. He felt he was seeing how different life was from art.  In art, all movements flow toward a collision.  The thought tired him.  It was quite involuntary, he later recalled, when he then closed the novel in his lap, slid down in his seat, and let himself feel how truly tired he actually was.