On the 6 August 2017, an Airbus A320, registered VH-VGY, operated by Jetstar Airways, was flying between Wellington and Christchurch in New Zealand.
Air traffic control had cleared the flight for a published arrival procedure followed by an instrument approach. During the arrival procedure prior to commencing the instrument approach, the aircraft descended 1,000 feet below the published altitude on the arrival procedure. Air traffic control noticed the descent below the arrival procedure altitude but did not alert the flight crew at the time. The flight crew had not been aware that their aircraft had descended below the arrival procedure altitude. Initial indications are that no terrain warning was generated by the air traffic control radar system or on the aircraft, nor did the aircraft descend below the segment minimum safe altitude published on the arrival procedure.
The investigation AO-2017-007, conducted by the Transport Accident Investigation Commission in New Zealand, is continuing.