Below are the main public transport operators providing passenger travel for getting around New Zealand:

Air New Zealand
International and national flights can be booked here. Air New Zealand put their cheapest fares for National flights on this website.

Qantas New Zealand
International and domestic flights within NZ can be booked here.

Origin Pacific Airlines
National (domestic) flights can be booked here.

Freedom Air
Budget trans-Tasman flights (between New Zealand and Australia) can be booked here.

The Interislander
Book your inter island ferry (between the North Island and the South Island) here.

Bluebridge Cook Strait Ferry
Ferry operator between the North and South Islands.

Intercity Coachlines
For bus travel throughout New Zealand.

Atomic Shuttles
For bus travel throughout the South Island.