There’s an entirely different world going on at 35,000 feet. The sky is full of highways, a single universal clock, and a language every pilot understands, no matter where they took off from. Your pilot isn't flying solo either. Air traffic controllers, the quiet masters of that hidden world, are working behind the scenes on every leg of your trip, long before you even board. If you’re curious to know what’s happening up there while you’re watching a movie and sipping some coffee, here are 10 things about air traffic control you’ve probably never heard.