The world's busiest airport isn't in the world's biggest city. It's in Atlanta, a great southern city that by dint of accident and capitalism sits, metaphorically speaking, at the center of the map.

More than 2,500 flights carrying 250,000 passengers pass through Hartsfield-Jackson Atlanta International each day, headed to or coming from 225 cities around the world. Delta, which carries more passengers than any other airline, accounts for 75 percent of that traffic.

In the first episode of WIRED's Flight Mode, we take you into Delta's "mission control," where nearly 300 people track every one of the hundreds of aircraft in the airline's fleet. Each follows flights through a different part of the world, using the world's scariest spreadsheet to monitor everything from the weather to maintenance issues to air traffic control, to keep everyone moving along smoothly.

It's thankless work, because if everything goes well, no one knows these people even exist. So the next time you take off without delay, mutter a word of thanks to these folks and their inscrutable spreadsheets.