LATEST: Fog that disrupted the travel plans of thousands of passengers in and out of Christchurch Airport today is clearing.
Airport spokeswoman Yvonne Densem said domestic flights were landing, and the first domestic flight to leave since 10am departed just before 2pm.
Two international flights are on their way and an international flight departed at 9.50am.
About 2500 Air New Zealand passengers were affected by this morning's fog, with the "persistent low-cloud conditions" forcing the cancellation of 18 return and nine one-way services, an Air New Zealand spokeswoman said.
The airline had arranged for an extra unscheduled return service between Auckland and Christchurch to help accommodate the disrupted passengers, she said.
"Air New Zealand will continue to monitor conditions and will resume normal operation as soon as practical," she said.
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Densem earlier said many delayed travellers were doing business by phone and email.
"We have free wi-fi, so they can continue to do their work,'' she said.
See the airport website for more details.
The chilly, still night also saw pollution levels breach maximum health guidelines in Christchurch for the first time this autumn. Two other breaches recorded this year were in February, when strong winds blew clouds of dust across the city.
Simon Cooper said he would have to cancel the first of four appointments he had booked in Invercargill today because his 9am flight had been cancelled.
The healthcare professional said he had to fly back to Christchurch at 6.15pm and would not have enough time to see all his clients now.
"It seems to be this time of year - winter. I've had a snow day in Invercargill [last year] and wasn't able to get out," he said.
One couple, who wanted to remain anonymous, said they were worried the delay would cause them to miss a connecting flight in Auckland to Hong Kong.
The couple were meant to depart at 8.40am, but had been shifted to a 9.45am flight.
Joel Davidson hoped to fly to Auckland at 9.45am after his 8am flight was cancelled.
"They haven't said anything yet. I'm hoping the sun's going to come out," he said.
He had been in Christchurch with about 20 co-workers for an event and all were now stuck at the airport.
The others would probably end up driving to their next job in Nelson instead of waiting for new flights, Davidson said.
MetService spokesman Daniel Corbett said warm temperature yesterday and a chilly night combined for the ''perfect recipe'' for today's fog.
"The sun warms the ground during the day and at night, that starts to radiate,'' he said.
"If you have a breeze, that warmth does not radiate away.''
Instead, the warmth built up into a thick layer of fog.
Visibility at Christchurch Airport was down to 200 meters, Corbett said.
It would take between two and three hours to clear, after which Christchurch was in for a mild day of about 17 degrees Celsius.
- The Press