At least 32 flights in and out of Wellington have been cancelled due to thick fog this morning, with one flight diverted to Palmerston North.
Many other flights have been delayed and more cancellations are possible.
All of the weather-affected flights are Air New Zealand services but two Jetstar flights to and from Christchurch were also cancelled due to mechanical problems.
The arriving flights affected are from Dunedin, Blenheim, Taupo, Westport, Nelson, Napier, Rotorua, Hamilton and Gisborne.
Flights departing Wellington to these same centres have also been cancelled.
Air New Zealand says the fog affected several flights which had flow-on effects to other scheduled flights.