Commercial airline flights have resumed over New Zealand after a radar outage resulted in planes being grounded and traffic controllers forced to guide in-air craft using radios.

The outage started at 14.41 local time (12:41 AEST) following an internal network failure at AirwaysNZ, a profit-driven state-owned enterprise that manages New Zealand's air traffic control systems.
As planes were able to land but not take off for two hours, delays built up and created a backlog of flights.
All airports around the country were affected by the radar outage, including the main hub at Auckland. A number of International and domestic flights were delayed and/or cancelled.
National carrier AirNZ said around 160 of the airline's international and domestic flights were impacted by the radar outage.
AirwaysNZ said it immediately suspended all non-airborne flights while it investigated the issue.
"At no point was the safety of any aircraft compromised," a spokesperson said.
"Throughout this outage we had back-up processes in place to deal with this eventuality safely. Around 50 airborne flights were directly affected."