Investigators have interviewed the pilots of an Air New Zealand plane that lost pressure, descended rapidly and deployed oxygen masks on Friday morning.
Five crew members and 76 passengers were aboard the Boeing 737-300 from Wellington to Auckland. The pilots immediately descended to a level where oxygen masks were no longer required.
The plane landed in Auckland with no further incident.
The commission says it has spoken to the pilots and looked at some flight recorder information but has yet to determine the cause of the incident.
Its investigators will resume examining the aircraft on Monday with help from Air New Zealand engineers.