Airways New Zealand's chief operating officer has shed further light on "network failures" that prevented flights across New Zealand yesterday.
Pauline Lamb said a trio of simultaneous failures lasting just four minutes were at the root of the problem, The further delay was caused by the need to test systems and make sure they were working properly.
"It was due to three events happening at the same time," Lamb told Radio New Zealand this morning. Radar and communications data distribution was affected.
"We isolated those events and as soon as we were able to verify the integrity of the system we were able to get it up again.
"Although it was a four minute outage we took some time to make sure the system was working correctly and testing it before we resumed operations."
Lamb said Airways wanted to investigate the incident thoroughly to ensure there was no recurrence.
The Transport Accident Investigation Commission (TAIC) is also taking an interest, announcing its own investigation this morning.
"A team of three investigators has begun the initial evidence gathering, working with the Airways Corporation and Civil Aviation Authority," TAIC said in a statement.
The outage is likely to blow a hole in Airways' up-time targets. In its 2014 annual report, the company boasted it had suffered no major system failures.
"System availability is 99.94 percent year-to-date with no major outages. None of the outages had any significant impact on commercial airline operations. Average delay is 13 percent ahead of target, with inflight delays for arrivals into Auckland International Airport improved by 63 percent for the 2014 calendar year," the state-owned company reported.
Lamb said backup procedures worked and investigations are continuing.