A passenger on a flight from Christchurch says they circled Auckland for an hour this morning as fog blanketed the city, preventing planes from landing and taking off.

26 flights have been cancelled at Auckland Airport so far this morning as fog disrupts both arriving and departing domestic flights.

International flights have so far been unaffected.

One passenger said his flight from Christchurch had circled Auckland for an hour before being diverted to Wellington.

Another person said they had been waiting in their plane on the tarmac at Auckland Airport for nearly two hours. They said their flight was supposed to take off at 7.15am but at 9am, they were still waiting.

Thirteen departing domestic regional flights have been cancelled, including services to Napier, Nelson, Palmerston North, Taupō, Gisborne, New Plymouth, Queenstown, Christchurch and Wellington.

Thirteen arriving domestic regional flights have also been cancelled, including services from Napier, Palmerston North, New Plymouth, Taupō, Gisborne, Queenstown, Christchurch and Wellington.

Two departing flights to Tauranga and Invercargill have been delayed.

Three domestic mainline flights to Queenstown have also been delayed.

International services have not been affected by the fog.

Fog restrictions came into effect just before 5am.