Watching a modern, massive, airliner taxi down a runway, slowly pick up speed, and then haul itself into the sky is one of the most impressive demonstrations of man-made engineering and ingenuity. Thanks go to the jet engine.

A pair of the things, slung underwing on a plane like a Boeing 777, provide enough thrust to push the aircraft and its hundreds of passengers aloft, spinning reliably for over 5,000 miles, day after day.

In the second episode of WIRED’s Flight Mode, we take you inside Delta's tech ops facility at Hartsfield-Jackson airport, where the airline's engineers tear down engines, put them back together, then run a battery of tests on them. In a facility the size of 47 football fields, these folks check everything from the huge fan blades at the front to the tiny components of the fuel injectors. Fun fact: That white swirly on the center of an engine isn't for decoration, or to scare birds. It's a safety feature for ground techs: If the engine's spinning quickly enough that you can't clearly see it, you know you're in danger of being converted to apple sauce.

Those men and women have to service engines for more than a dozen kinds of planes, made by Airbus, Boeing, and McDonnell Douglas. But they apply the same rigor to each powerplant they reassemble before bolting it back onto a plane. That means hauling it down to a concrete bunker, hanging it from a test rig, and spinning it up to full speed while technicians measure its vital statistics and check for leaks.

While the staff in charge of Delta's testing hope nothing catastrophic happens, the engine's designers deliberately aim for the worst case scenario. To certify an engine, they fire everything from sand, to ice, to already-dead chickens into their machines to make sure they can handle failure in a controlled manner.

This sort of maintenance and testing is the reason a jet engine is likely to go 30 years between failures, compared to 365 days back in the 60s. Which is a very good thing when you realize that they propel 100,000 planes to perform the impossible every single day.