Auckland Airport is resisting pressure from a community group to soundproof homes under new flight paths north of Manukau Harbour.
It wants to confine a multimillion-dollar "acoustic mitigation" programme to properties within existing and proposed noise contour zones closer to the Mangere-based airport.
The airport company and residents opposed to new curved flight paths promoted by the aviation industry as more fuel efficient than existing linear approaches have been in mediation this week, in an effort to find common ground before independent commissioners report to Auckland Council on its 30-year Unitary Plan.
About 4000 homes are already within noise zones near the airport, which the company acknowledges in "contingent liabilities" reports to shareholders could ultimately cost it up to $9 million for mitigation treatment such as double-glazing.
Hundreds of homes and some schools have already been treated under an agreement ratified by the Environment Court in 2001 between the airport company and the former Manukau City Council. The company pays about $300,000 a year into a community trust overseeing that effort.
The company is now seeking from Auckland Council an extension of noise contours out from a second runway which it wants to open by 2028 to the north of its existing operation.
Although the Manukau District Plan included contours for a 2150m second runway, the company wants to be able to lengthen it some time after 2044 to 3km.
That compares with the 4km length of its existing runway.
But it says most land in the more intense of three expanded noise areas it has proposed to the council is either owned by itself or zoned commercial.
Corporate affairs general manager Charles Spillane told the Herald the number of extra homes needing noise insulation after 2044 was likely to be "in the low hundreds".
Although most would be in Papatoetoe, airport development chief Graham Matthews said night air movements to and from the east of the second runway would be banned.
A first stage of the second runway was to have been open for domestic flights by now, after a ground-breaking ceremony in 2007, but the project was interrupted when airlines were hit by the global financial crisis.
The company has since decided to develop it for short-haul international services as well.
Residents group The Plane Truth is meanwhile asking the council to extend soundproofing requirements further through the Super City.
It wants an amendment to the proposed Unitary Plan "requiring appropriate acoustic mitigation to be provided for houses which are suffering significant and unreasonable noise effects as a result of the new flight paths".
It also wants membership of an aircraft noise community consultative group expanded to include residents of affected suburbs throughout Auckland.