Riders were stuck on the "Sky Trek Tower" ride for more than two hours Sunday at Six Flags Great America in north suburban Gurnee.
Passengers told NBC Chicago they had made it to the top of the nearly 30-story ride when it got stuck. The ride remained unmoving for about an hour before it started moving down, then plummeted about 20 feet before becoming stuck again, according to riders.
"It was mostly parents trying to keep their kids calm," said one rider. "Obviously when it suddenly dropped there was a lot of screaming, shouting and crying."
Six Flags Great America said the ride would be closed for inspection before reopening.
"Sky Trek Tower operates just like an elevator. The elevator-style secondary brakes serve as a safety mechanism to stop the cabin at any point along the tower," the park said in a statement. "During the manual descent, the secondary brakes engaged, causing an immediate and abrupt stop of the cabin. At no time did the ride drop at a high rate of speed. All guests were safely escorted off the ride via a staircase by our rides management staff. Because the safety of our guests is our number one priority, we took the time necessary to safely exit the ride."
Inspectors were expected at the scene Monday morning.
The ride, described as a rotating, aerial cabin, offers riders a view of the Great America skyline from 28.5 stories in the air, according to the amusement park's website. It was introduced at the park in 1977.