Air New Zealand's direct flight between Wellington and Invercargill will soon be no more. 

It's being scrapped, with its last service in mid-January.  

Great South chief executive Chami Abeysinghe says customers are still able to fly to Wellington via Christchurch, and the airline's adding more flights between Christchurch and Invercargill. 

She told Ryan Bridge there's multiple factors for the decision including softening domestic demand and engine issues. 

Abeysinghe says one of the key factors is ensuring accessible flights between the main centres. 

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