ABC7 spoke with frustrated passengers waiting to be transported on shuttle buses, and even school buses, at Terminal 1.
When the automated train's service first went out, there were large crowds of people trying to figure out how to get around the airport. That train takes people from terminal to terminal.
O'Hare's Twitter account said service was resuming at 8:17 p.m., but asked travelers to allow extra time to get around the airport.
The video in the player above is from a previous report.