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Auckland International Airport says fog could cause a second day of disruption tomorrow, and would-be travellers should check flight conditions before heading to the airport.

Fog caused havoc at the airport today, disrupting flights and delaying passengers for several hours.

At least two international and six domestic flights were affected by the fog.

With morning fog again forecast for tomorrow, the airport tonight urged travellers, and those either meeting or seeing people off to check before setting out.

Airport chief executive Don Huse said that at 6.15am today the runway was clear but within 15 minutes the fog had moved in so these events can cause disruption at relatively short notice.

"With that in mind and given that tomorrow's weather forecast suggests similar disruption to schedules could be repeated we would urge all those travelling, meeting or farewelling people at the airport to check with their airline that things are running to time."

Mr Huse said fog could be a highly localised phenomenon and conditions at Auckland airport could be quite different from where people set out.

Fog generally affected the airport for some part of the day on about 12 to 16 days of the year with flights having to be diverted on anything from three to 11 of those days.

"Every effort is made to take advantage of breaks to enable aircraft to land or take off but public safety remains paramount. Today, the lack of wind also compounded the issue," Mr Huse said

A new air navigation and lighting system was being progressively implemented from July this year.

The system would enable aircraft to land during foggy conditions and was expected to be fully operational by May 2008.

"Once in place, Auckland is expected to be the first airport in Australasia to have such a system."

Last July 1400 international travellers were stranded in aircraft at Ohakea when Auckland was blanketed by fog, leaving some grumpy passengers in their seats for an extra eight hours.

Passengers complained there was no food, drink ran out and some aircraft toilets became blocked.

International flights that cannot get into Auckland generally try to divert to Christchurch but they go to Ohakea if they haven't got enough fuel. In July Christchurch airport was also affected by fog.