"The cable just jumped a wheel, but the gondola was in no danger of falling," said Assistant Fire Chief Thomas Haring.
Firefighters and police officers used a crane to rescue a family of three from the offline gondola, which swung about 100 feet in the air. They got the gondola back online and restarted the system, allowing the passengers in the other cars to complete their rides before getting off.
The cable car ride broke down around 5:30 p.m., Wednesday, halting 14 cars.
Thirty adults and seven children were stranded.
A 14-year-old girl, her mother and another adult relative were plucked from the offline Skyfari gondola around 8:15 p.m., police said. The other 34 people stepped off the cable cars at about 10:20 p.m.
The mother, Olga Perez, said she was visiting the zoo from her home in suburban New City with relatives from Colombia, who were stranded in other cable cars with her terrified 9-year-old son. She said firefighters talked to them and gave them water.
"We were trying to calm ourselves," she said. "Deep in my heart I knew I was going to take it a little bit at a time."
The Skyfari, which passes over the butterfly garden, the baboon habitat and part of the African plains exhibit where lions and gazelles roam, offers visitors a bird's-eye view of the celebrated zoo and its surroundings. Each of its gondolas can hold up to four people.
Zoo officials and rescuers, who used a crane brought from Queens, said they didn't know why a cable car had become misaligned.
Police Commissioner Ray Kelly said stormy weather might have contributed to the mishap.
The Skyfari, which opened in 1973, is certified for operation by the state Department of Labor. A department spokesman didn't immediately reply to an e-mail or a telephone message left at an after-hours number.
Zoo Director Jim Breheny, who joined Kelly and other officials at a news conference after all the passengers were rescued, said the ride's cables and pulleys are serviced every year.
"It was an unfortunate incident, but it was a happy ending to an unfortunate incident," he said.
Kelly said a seven-months pregnant passenger complained of cramps and was taken to Jacobi Medical Center. One other passenger was examined but refused medical attention.
In April 2006, both cars on an aerial tramway that shuttles commuters and tourists between Manhattan and an island in the East River stopped moving because of mechanical problems. The breakdown stranded 69 people for about 11 hours.
Police staged a daring rescue, going up in a diesel-powered gondola to reach the cable cars, which offer breathtaking views of the city from up to 250 feet high, and removing the passengers a few at a time.
The Roosevelt Island cable car system, featured in the movies "Spider-Man" and "City Slickers," was repaired and upgraded.
