You fly to NI from Australia with Air New Zealand.  There are flights to/from Sydney each Friday and Monday, and from Brisbane each Saturday and Tuesday.  There is also a flight from Auckland each Sunday, although this will change to a Saturday flight from June 2017.

Flight times are as follows:

To/from Brisbane – 2 hours 30 minutes

To/From Sydney – 2 hours 45 minutes

To/from Auckland – 1 hour 45 minutes

There are also several travel agencies – Burnt Pine Travel, Travelworld, and the Travelcentre – who can book flights to anywhere in the world if travel is your passion.