"It is understandable Barnz is not aware of its members routes strategies. It is common for airlines to avoid publicising their future route development plans.''
Councils, which own about one-third of the airport company have allowed for $150 million in their long term plans should the work go ahead.
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A study done for the airport shows that extending the runway could yield $1.75billion in direct benefits for New Zealand between 2020 and 2060 and $684 million for the Wellington area in the same period.
But Beckett said more study needs to be done.
"Committing millions of dollars of ratepayers' money to the extension of Wellington Airport's runway is premature. The economic work done around the extension by EY (Ernst and Young) is seriously inadequate for making those commitments - although useful for promoting the proposal," he said.
A cost benefit analysis - where the benefits are compared to what would happen without the extension - was required. An NZIER study commissioned by Barnz confirmed this.
"People in the Wellington region, who will fund a lot of the extension, deserve better," Beckett said.
He said said it was not a matter of airlines being against the extension, but more about concern over the cost of it.
"The ultimate failure would be that the cost of the extension would either fall on ratepayers, or in higher costs for people flying into and out of Wellington Airport on all services."
The biggest Barnz member, Air New Zealand was consolidating more of its operation around Auckland Airport - where big expansion was planned - but Beckett said this was not driving the association's stance.
The runway at Wellington Airport is now 2081m and the airport says it needs to be at least 2300m to attract long haul services.
Besides Air New Zealand, Barnz represents Qantas, Jetstar, Virgin Australia, Emirates, Singapore Airlines, LAN Airlines, Cathay Pacific, China Southern, China Airlines, Malaysia Airlines, Korean Air, Thai Airways, Fiji Airways, Air TahitiNui, Aircalin, Tasman Cargo Airlines, Air Vanuatu, Menzies Aviation, Fieldair and Airwork.
See the Barnz NZIER report here: