A Qantas jet flying from New Zealand to Australia was forced to turn around when the cabin started to lose air pressure, the airline said in a statement, Reuters reported.
The Australian carrier has an excellent safety record but has come under scrutiny over the past year after its aircraft experienced a series of technical problems in flight.
Qantas said Saturday's incident involved a Boeing 737-400 ascending out of Auckland en route to Brisbane. At 25,000 feet it developed a "subtle pressurisation problem," the airline said.
The aircraft landed and all 91 passengers disembarked safely. The plane is being examined by engineers.
"The cabin was depressurizing at a controlled rate but certainly not rapidly or noticeably to passengers. There was never any imminent threat to passengers, the crew or the aircraft," the airline said in the statement.