Air New Zealand may seek compensation for the disruption to its flights caused by Thursday's air-traffic control outage at Dunedin International Airport.
Air-traffic control was suspended on Thursday evening because the sole-charge controller called in sick.
The airport has six controllers.
Air NZ spokesman Mark Street said the airline would discuss the matter with the Airways Corporation, which manages air-traffic controllers, to find out what went wrong.
Air NZ had to divert two Boeing 737 jets, carrying a total of 237 passengers, to Invercargill, where the passengers were offered buses to Dunedin.
The planes returned to Christchurch on Thursday evening, and one flew back to Dunedin early yesterday.
The airline used an ATR-72 turbo-prop plane to replace the jets on the Dunedin-Christchurch service.
Air NZ allows turbo-props to fly into airports with unmanned control towers.
Airways Corporation spokeswoman Nikki Hawkey said a former Dunedin air-traffic controller working at Christchurch Airport had been transferred to Dunedin to relieve for three days while the sick controller recovered.
Air-traffic controllers have site-specific licences, so only controllers with licences for Dunedin can work at the airport.
Controllers take between six and 14 months to train, depending on the airport.
The Christchurch controller was working on Thursday, so could not be brought south sooner.
The last outage of air-traffic control in Dunedin was 11 or 12 years ago, she said.
Airways had a good service record and no internal review of rostering practices was planned.
Dunedin International Airport chief executive John McCall disputed it was over a decade since an outage, saying flight disruptions three or four years ago prompted the corporation to boost the pool of Dunedin air traffic controllers from four to six.
Mr McCall said he felt reassured by discussions with the Airways Corporation yesterday.
Airways chief executive Ashley Smout had reassured him the rostering system was robust.
He said Mr Smout acknowledged there was an issue three to four years ago.
Questions remained for Mr McCall about how Thursday's situation developed and he looked forward to a fuller explanation.
