Wellington International Airport may have been breaching safety regulations for more than four years pending a ruling from the High Court on its proposed runway extension.
The New Zealand Air Line Pilots' Association (NZALPA) has sought a judicial review for a Civil Aviation Authority decision to approve a shorter run-off area for the proposed project which could endanger public safety, it said.
ALPA's barrister Hugh Rennie QC says they believe that the Civil Aviation director has agreed to a 90 metre runway end safety area, or RESA, and have stop consulting with the union.
The international recommended standard is 240 metres.
Much of the case is centred on the phrase "if practicable" in the aviation code, which has been used to determine whether the CAA is permitted to make a decision using financial costs as a metric.
The CAA maintains it has not yet made a decision and remains open to consultation.
"Costs, like any other pragmatic consideration is relevant to what is practicable," CAA barrister Francis Cooke QC told the Wellington High Court on Monday.
"If that's what really the law requires then it should have been done some time ago."
Wellington International Airport has only ever had a 90 metre RESA and would have been in breach of the standard since 2011.
A RESA is an area clear of obstructions where plane can pass if they overshoot the runway when landing or before taking-off.
Earlier, the court heard the case was not a "us versus them" scenario according to ALPA barrister Mr Rennie, but a judicial decision is required to clear the issue for all three sides, ALPA, the CAA and Wellington International Airport Limited.
He contended the director of the CAA put the economic consideration of the proposed extension before passenger safety and the cost/benefit should not have been a consideration.
"The director has allowed himself to be persuaded that the airport company thinks it would be a bit too expensive to provide the 240 metre RESA, or anything greater than 90," Mr Rennie said.
The issue could have widespread ramifications as the court's decision could be used as a domestic and international precedent.
Wellington International Airport has been investigating the possibility of extending the runway by 300 to 350m to attract long-haul flights to the nation's capital. The pilot's union have previously said the approach to Wellington Airport is difficult with heavy turbulence as well as hills on the flight paths to the runway.
The hearing continues.