Atlanta’s Hartsfield-Jackson International Airport lays claim to the title of maintains claim world’s busiest airport—as it has for the past 19 years. The massive airport processes more than 100 million passengers each year with help from the world’s busiest airport train system, which moves people through the nearly 7-million-square-foot complex.

Hartsfield-Jackson’s autonomous people mover, dubbed the “Plane Train,” runs underground, connecting the airport’s seven concourses with domestic and international terminals. This trusty system has been running for nearly four decades since it first opened in 1980. The Plane Train consists of eleven four-car trains, which operate on a three-mile loop track. The trains work hard, running every two minutes and carrying more than 250,000 passengers per day.

As the fastest route between concourses, it’s critical that the Plane Train work flawlessly to help passengers avoid travel delays. That’s a big responsibility that falls to Christopher Smith, the airport’s aviation transportation systems manager. Field Service Digital spoke with Smith about what it takes to keep the world’s busiest train system moving.

Who keeps the Plane Train running?

Smith: Bombardier is the current operation and maintenance provider for the Plane Train. The service team is made up of 120 employees spread out over three shifts. The first and second shift perform preventative and corrective vehicle and system maintenance. The third shift performs station door, rail switch and track maintenance using a standard mechanic toolkit. The only time the Plane Train is not running is during system-wide maintenance and track inspection, performed between 1:30am to 4:30am.

What repairs does this team handle?

Smith: They are primarily responsible for repairing station doors, vehicle doors, brakes, tires and power collector shoes [devices that draw electrical power for the train]. The team is also responsible for safety testing. This includes testing vehicle communication, vehicle braking, vehicle door operation, station door operation, and switch communication and operation.

What happens if the people mover at the world’s busiest airport goes down?

Smith: We move more [people] than any other airport in the world, and [the train system] transported approximately 93 million passengers last year. One time, one of our main power feeds failed, which temporarily took down the train system. The hour-long delay affected flights here at ATL and had an impact on flights across the nation.

What’s next for the Plane Train?

Smith: There are plans to construct a crossover behind baggage claim, which will help create a shorter interval between trains. The track extension will also allow more cars to be added, which will increase passenger capacity.