Six flights in and out of Dunedin were cancelled this morning because of heavy fog, affecting 430 passengers.
Most passengers have been switched to other flights, but some were taken by bus to Christchurch.
Dunedin International Airport was closed until 10.35am when skies cleared.
Air New Zealand airport manager in Dunedin Alistair Bevin said flight schedules are now back to normal.
An early morning flight from Christchurch to Dunedin was turned away due to low visibility, and because there was also thick fog at Christchurch International Airport, the Air New Zealand ATR was sent to Nelson - one of the only airports not covered by fog.
Several flights were also circling South Island airports waiting for visibility to improve.
Invercargill and Queenstown airports were also covered in fog.
Metservice forecaster Richard Finnie said the fog was not expected to lift until midday.The fog has also stopped flights in and out of Wellington.
Wellington Airport services officer Gavin Short told NZPA said flights stopped about 8.30am.
"It looks like it's here to stay for a while," he said.
The fog was also posing problems for motorists, with police warning those in the city's northern suburbs and the upper Hutt Valley to take care.
Motorists should drive with their lights on and watch following distances, and cyclists should take special care, Inspector Steve Darroch said.
