Zoo officials say people were stuck for 30 minutes before they were able to fix it.
"Scary and we're up there and, you know, it's windy here in Oakland today, so it's swinging."
Fairfield resident Teresa Michel was shaking and crying as she exited the Oakland Zoo with her children.
She was up in a gondola at 2 p.m. Friday. The gondola runs from the old original zoo up a hillside to a café and a brand new California Trail section that just opened Thursday.
When the gondola stopped, stuck riders started calling the zoo on their cellphones.
"They say the fire department is here, don't worry, we're going to evacuate you. I said how are you going to evacuate us, oh we have ladders. We're at the top. Over three stories and I've got a daughter in a wheelchair," said visitor Teresa Michel.
Some tweeted photos describing "humans stuck in gondola cages." In one photo, you can see 100 people waiting at the top, including groups of children.
Many had to walk down a fire road to exit.
For those who were stuck, after 30 minutes swaying above the zoo, the state-of-the-art gondolas finally took passengers down to the ground.
Zoo officials say the one-year-old Swiss-made ride had a digital glitch that cause the system to power down unexpectedly.
Like a computer, they were shut down, rebooted and tested before riders were permitted back on later in the afternoon.
"No one was ever in any danger," said Oakland Zoo spokesperson Erin Dogan Harrison. "It was just a huge inconvenience and we apologize to our guests for what they experienced here today."
"It was fine," said visitor Norma Aguayo. "There's air, there's a breeze. She threw up because she's scared of heights. But it's not the zoo's fault. They're trying hard."
They doled out free passes and even t-shirts and hats to those who were traumatized by the experience.