Staff in the national air traffic management centre lost contact with all aircraft in New Zealand's skies for four minutes one afternoon in 2015.
National air traffic controllers lost radar and radio contact with all aircraft in the skies above New Zealand for four minutes one afternoon in June, 2015, an investigation has revealed.
A Transport Accident Investigation Commission report, released on Thursday, outlined that a blackout ensued when a programme software upgrade inadvertently caused a "broadcast storm" on June 23, 2015.
"The storm prevented normal digital data traffic from reaching the control centre and thereby interrupted radar surveillance and communication systems," the report says.
It only lasted four minutes, but, in that time, contact was lost between the sector controllers at the national centre in Christchurch and airport control towers around the country.
"Although the sector controllers had alternative radio frequencies and standby radios to contact aircraft, not all of these systems worked as expected."
The commission concluded that the broadcast storm subsided quickly and normal air traffic services resumed in the following hours.
An external review of the error found that the Civil Aviation Authority did not have the right capability, but the commission was satisfied this had now been rectified.