Airways New Zealand says it is working with Telecom to ensure there is no repeat of the communication failure that stopped air towers from communicating with planes on Friday.
Up to 60 planes were in the air when the radio network that allows air traffic control and pilots to communicate went down for about 15 minutes.
Telecom says the problem occurred just after 1pm and was due to a brief failure of the core network, which has been fixed.
Airways resorted to a back-up satellite system so it could continue communicating with pilots.
It says it is expecting answers from Telecom in the next week about why the system stopped working.
Airways says the last similar incident appears to have happened 13 years ago.
During the outage, planes due to depart were held on the ground as a safety precaution. The situation caused flight delays at mostly North Island airports, including Auckland and Wellington, as well as regional airports.
Services south of Wellington were largely unaffected, although flights were held back as a precaution in Christchurch despite no communication problems occurring there.