Two Jetstar pilots have been stood down and an investigation launched into a flight to New Zealand earlier this month.
A spokesman for the airline today said "the wrong flap position" was selected as the flight from Sydney prepared to divert away from its destination of Christchurch on June 3.
The plane was involved in an aborted landing at Christchurch due to bad weather and instead landed in Auckland.
The flap position was "quickly fixed", the spokesman said.
"Jetstar understands the significance of this and is completing an assessment of exactly what happened and why," he said.