Air New Zealand's chief executive says it is possible to build a second commercial airport in Auckland for $200 million.
The airline has revealed it is in the final stages of assessing the viability of flying commercially from the Defence Force airbase at Whenuapai.
Air New Zealand has not yet discussed its proposal with the government or Defence Force.
The NZDF airbase was used as Auckland's main airport until until it was supplanted by the Mangere site in 1965, and chief executive Christopher Luxon said there was a strong case for it as an alternative.
"The real motivation is you can't sit in a country where we've over the last five years had three million more passengers go through Auckland Domestic airport and nothing has changed in the size of that terminal since 1966.
"Walking on a blue line might have been great in 1985 going from domestic to international. In the rain it's not particularly fun for an international visitor coming to New Zealand and saying 'is this a world-class place?'"
Mr Luxon, who will stand down as chief executive this month, expected it could cost between $100m and $200m to build passenger facilities at the Whenuapai base with funding help from a consortium of infrastructure companies and iwi.