"Contrails" are those silvery white tracks left in the sky by the engine exhaust condensation of high-altitude aircraft. They show where the airborne traveler is going, as well as where he has been. They define the journey, conducted at high speed, where the air is thin and danger is always lurking. This was the harsh testing-ground for a father and his son, from a family of Swedish immigrants---unlikely participants in the armed conflicts that would...