A Jetstar flight landing in Christchurch dropped below the minimum height allowed while on descent into Christchurch, the Transport Accident Investigation Commission has determined.
The incident occurred on just before 7pm on August 6, 2017 when an Airbus A320 with 128 passengers and six crew was in the final stages of preparing for landing.
"During the arrival procedure the aeroplane inadvertently descended below the 2,500-foot minimum safe altitude for part of the arrival procedure," the TIAC report says.
"The infringement was noticed by the air traffic controller at the time, but the flight crew was not advised until the aeroplane had landed. The aeroplane landed safely."
The TIAC says the aircraft descended below the published minimum safe altitude for a portion of the arrival path into Christchurch Airport "because the flight crew did not maintain adequate situational awareness of their aeroplane's location in relation to the standard arrival route".
The commission also found Jetstar's arrival procedures didn't encourage the appropriate use of the Airbus' automated navigation systems and the aircraft and it was using an 'open descent' mode rather than the fully automated 'managed descent' mode which was available which allowed for the aircraft to drop below the 2500 foot height.
A spokesperson from Jetstar told Newshub the airline has made changes to its policies since the incident.
"For a short time upon descent into Christchurch a Jetstar flight, operating under radar control and direction, flew below the published minimum safe altitude."
"While this incident didn’t impact the safe operation of the aircraft, or impact the flight path of other aircraft, we take it very seriously."
"Since this occurred we have revised our Pilot Monitoring policies to enhance pilot awareness during all phases of flight."
TIAC also found the air traffic controller failed to follow required procedures after witnessing the aircraft fly below the minimum height buy not alerting the flight crew until after it had landed.
Tim Boyle from Airways New Zealand says they welcome the TIAC's findings.
"It is important to note that TAIC has made no recommendations for change. We pride ourselves on having a culture of continuous safety improvement and, in any event like this, we take a close look at the surrounding circumstances to proactively identify opportunities for improvement."