Port Authority of New York and New Jersey spokesman Steve Coleman says Flight 9 landed safely Sunday afternoon about an hour after it left Newark.
Houston-based Continental Airlines Inc. says 291 people were on board.
No injuries were reported. The Boeing 777 wasn't damaged.
Federal Aviation Administration spokeswoman Kathleen Bergen says the pilots burned off and dumped fuel to make the airplane lighter before returning to the airport because of "a hydraulic problem."
Continental says the plane will be inspected to determine the cause.
In January, a United Airlines jetliner scraped its belly on a Newark runway after part of its landing gear failed to deploy.
