Auckland Airport is blaming ''extreme'' IT network congestion which led to flight delays after some services were knocked out, including baggage check-in.
Passengers faced delays through most of Saturday after intermittent faults to systems including telephone, radio, baggage and Wi-Fi reliant services.
The airport said it was forced to mobilise ''contingencies'' to ensure passenger baggage could be processed and continues work to make sure faults don't happen again.
The network issues were identified at 4am and fixed before midnight on Saturday.
The problem was tracked to four analogue voice gateway switches on a peripheral network - not the core network.