Webber says her group will take the airport to court based on several grounds ranging from noise pollution, to dust management and "vastly increased" traffic congestion.
She also says the plan shows "no commitment" to New Zealand's goal of carbon neutrality by 2025.
But Jenna Raeburn, the general manager of corporate affairs for Wellington Airport, disagrees.
"Our current space constraints mean aircraft can wait longer for gates, increasing fuel burn; and we have limited capacity to cater to the needs of low emission aircraft in the future. For example, electric aircraft will be smaller and more numerous, requiring more aircraft stands; and hydrogen and sustainable fuels will require additional infrastructure."
The expansion will allow room for aviation growth, but limit emissions.
Raeburn told the Herald any plans must be approved before work can begin.
"The expansion is not imminent. The designation supports our Masterplan, which provides the community with certainty as to how the airport is likely to be developed over time. Approval of outline plans will still be required before any work begins."
She says having an accessible airport close to the city presents benefits like accessibility and proximity to events – but action will be taken to lessen the impact on nearby homes regardless.
This includes ensuring there is still a "buffer zone" between the airport and neighbouring homes, providing noise mitigation to those closest and putting limits on airport noise like engine testing.