Arrival - There are around a million people airborne at any one time. But what goes up must come down - and getting passengers safely back to earth depends on complex global networks and some astonishing technology.
Getting on the ground safely takes an army of hidden experts and incredible technology.
We take it for granted, but on any journey a hidden army of people keep your plane safe.
What does it take to get 100,000 flights a day ready for take-off and up into the sky?
About City in the Sky
At any one time, there are a million people airborne somewhere in the world. That equates to an entire airborne city - a city in the sky. So what does it take to run a "city" at 30,000 feet? In this series, we set off around the world to uncover the invisible global networks and complex logistics that make it all possible.
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