A $300 million extension to Wellington Airport's runway may have already been delivered a blow.

The Wellington Mayoral Forum has approved funding for half the cost, but wants a long-haul service to fly from the airport when work's completed.

But Air New Zealand has already ruled out operating a long-haul service from Wellington.

Wellington's deputy mayor Justin Lester says that's not a barrier.

"Not at all, I mean that could always change. Air New Zealand's current model is to fly out of Auckland, use it as a hub. They don't want to fly out of Wellington but there are other carriers that will."

He says Fiji Airways already flies internationally from Wellington, and they're in talks with other carriers about jumping on board when the extension's done.