As I understand it, it is a roundabout way of paying partly in airpoint dollars and partly in real dollars - if you can just buy the airpoint dollars 'dollar for dollar'. Before this came in, you had an 'either/or' option when buying flights on line - use one or the other, but not a partial mix of APD and $$.

So it means if you are sitting on say $35 airpoint dollars and want a fare priced at $200, you can actually use up the amount in your airpoint dollars account ($35) and pay the rest ($165) using POLI or credit card..

Effectively, it means you don't save to wait and wait for your airpoints to accumulate until you have enough for a flight - this would be useful for someone where they have some airpoint dollars and not much future travel planned on NZ - they can 'clean out their account'.