Book excerpt: Nick Selig excavates the highways to the sky that have been covered up by urban sprawl or dissolved by neglect. More than a guide to landing strips that have had startling second lives as shopping malls or retirement homes, he uncovers the excitement of the early days of air travel, when a man might cling to his job as a lavatory truck driver for a closer peek at aviation. In this follow-up to "Lost Airports of Chicago," discover how a tractor swap gave birth to Clow International Airport and revel in the daredevil exploits of puddle-jumper pilots over the wide-open spaces of Harlem Avenue.