Typhoon alert for Air New Zealand's Auckland to Shanghai flight

Typhoon Jongdari has already caused damage and travel disruption in Japan. Photo / AP

Air New Zealand has warned a typhoon that has battered parts of Asia could disrupt its flight to Shanghai tomorrow.

The airline said it is continuing to monitor what is now tropical depression Jongdari which is forecast to reach Shanghai later today.

In Japan tens of thousands of people had been ordered to evacuate ahead of the storm, power was cut to thousands of homes and dozens of people were injured.

Air New Zealand says on its Travel Alert page that there was a possibility that tomorrow's flight NZ289 from Auckland to Shanghai, may be disrupted.

"If your need for travel is not urgent, we recommend delaying your travel to a later date," the airline warned in an alert last night.

It says any affected passengers should call its contact centre.

"Please note, all incidental costs and penalties such as accommodation and/or meals are the customer's responsibility and should be referred to your travel insurance provider."

It could be the second weather disruption for the airline in two days.

Today fog in Auckland resulted in 31 flights cancelled or delayed, including those of other carriers.

Auckland Airport lifted fog restrictions at 8.21am after having them in place since 1.30am.

In that time 19 domestic flights were cancelled and 12 delayed due to the fog.

International and jet flights were not affected by the fog because there is sophisticated equipment to allow jets to land in very low visibility.

Air traffic controller Airways says at Auckland Airport it has a Category III Instrument Landing System (ILS).

The ILS sends out a signal which guides aircraft down onto the runway. It is always in operation at the airport but becomes even more important when pilots haven't got a clear view for landing. For a pilot, they may not see the runway until they actually touchdown.

The ILS along with an enhanced airfield lighting system ensure long haul flights can land.

When visibility is low Airways requires fewer aircraft moving around the airport to ensure nothing interferes with the ILS signal. This means spreading out the spacing between landings and take-offs, which slows things down.

Most turboprop aircraft do not have this equipment, and this is why fog mostly affects regional flights, Airways says.