Up to 60 planes were in the air when the radio network allowing air traffic control and pilots to communicate went down on Friday.
Telecom says the problem lasted for about 15 minutes just after 1pm and was due to a brief failure of the core network, which has been fixed.
The situation caused flight delays at mostly North Island airports, including Auckland and Wellington, as well as regional airports.
Control tower operator Airways New Zealand says a back-up system was used to guide planes already in the air.
General operations manager Lew Jenkins says satellite radios was used to guide the aircraft.
Planes due to depart were held on the ground as a safety precaution.
Services south of Wellington were largely unaffected, although flights were held back as a precaution in Christchurch despite no communication problems occurring there.