A “mechanical failure” halted O’Hare International Airport’s “people mover” transit system for about seven hours Sunday, according to the Chicago Department of Aviation.

Officially known as the Airport Transit System, it operates between all O’Hare terminals. It’s a relatively new system, having been unveiled in November 2021, after a three-year delay.

Sunday’s outage occurred on a train stationed at Terminal 3, the department said.

Shuttle buses were provided to get passengers to and from terminals, according to the department. The source of the failure remains under investigation.

“The CDA apologizes to any O’Hare passengers and employees who were inconvenienced by Sunday’s service interruption,” the department said in a statement.

When the new “people mover” was unveiled, it was almost three years behind schedule and four years after the shutdown of the old system.

The new cars are longer, enabling the system to carry 4,800 passengers per hour, almost twice as many as the previous one. 

And with 2,000 more feet of track, the new people mover includes a station at O’Hare’s Multi-Modal facility, near economy parking lots and the airport’s rental car facility.