Oxygen masks dropped automatically for the 76 passengers and five crew members aboard Air New Zealand flight NZ414 from Wellington to Auckland, Radio New Zealand reported.
"It's not a dangerous situation but it's one that has to be executed quite quickly in order to get the cabin down to a safe altitude. There's a limited amount of oxygen (available in the masks), about 12 minutes," said David Morgan, the airline's chief of flight operations.
The plane arrived in Auckland without further incident and was taken out of service. The national Transport Accident Investigation Commission will study its flight recorders, Air New Zealand added.