This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book focuses on events that have led to the closure of airspace to civilian operators, as well as innovations for eliminating them where possible, and minimizing the impact where not. The first decade of the twenty-first century ushered in the era of the ultra-long-haul flight. And yet, the longest of them Singapore Airline's record-setting 18.5 hour non-stop from New York to Singapore is gone the victim of recession and high fuel costs. The Middle East, comprising an ever-larger portion of global air traffic, has seen critical sections of its airspace Iran, Iraq, Syria closed at one time or another, causing a major logistical bottleneck to aircraft transiting the region. Technology takes their far, but there will remain daunting obstacles to the free and economical movement of commercial air traffic.