At any one time, there are around one million people airborne somewhere in the world; that equates to an entire airborne city—a ‘city in the sky.’ Straddling whole continents, the fabric of this extraordinary construction consists of the 100,000 flights that crisscross the world every single day. Take off around the world, on the arc of an actual journey from departure to arrival, to uncover the invisible global networks and complex logistics that make it all possible. Discover how aircraft are prepared for takeoff; examine what happens in flight, and look at what it takes to bring flights safely back down to earth. Travel from the coldest airport in the world to the busiest, and to the airport that is one of the most dangerous at which to land, to gain real insight into the nature of the global aviation network. This fascinating world has transformed the way we live in the 21st century, and our modern way of life would simply not be possible without the city in the sky.