Wellington Airport has been virtually brought to a standstill because of fog that's enveloped the city for much of the day, leading to the cancellation of dozens of services.
Most arrivals and departures through Sunday afternoon and evening were grounded, and flights on Monday morning could also be affected.
MetService meteorologist Kyle Lee says the fog is expected to hang around overnight. He says parts of the capital cleared briefly this evening, but that's not expected to last.
"It looks like tomorrow morning early, it's still going to be around, but then sort of about 8 to 10 it should start improving."
Earlier Air New Zealand said its smaller, turboprop regional flights were the only ones being affected, but further cancellations included larger planes travelling to the main centres, and to Australia.
Several of the regional turboprop flights were forced to return to their point of departure.
Air New Zealand's website also says they are continuing to keep a close eye on Tropical Cyclone Tino, which lashed Tonga on Saturday night.
"Based on current forecasting, we are anticipating disruption to our flights to and from select Pacific Island ports."
Wellington Airport is asking passengers to check their website for latest flight updates.