Wellington Airport has hosted its first public consultation on the runway extension.
About 65 people attended today's session to speak to experts about the project, with some questioning why so much public money would be needed for it.
The extension may cost tax and rate payers the majority of the $300 million price-tag.
The airport says the extension will result in an extra two-billion dollars for the country after costs.
But resident and economist, Ian Harrison, says the benefits are overstated.
"If the airport company truely believe their own numbers, they would go gangbusters and pay for it themselves," he said.
"The fact is, they're not prepared to put up their own money suggests they don't really believe the numbers."