Air NZ OneUp programme allows passengers to bid for a cabin class upgrade on flights. Eligible for an upgrade is economy and premium economy class ticket holders who had booked directly with Air New Zealand either online, through its contact centre, or at an Air New Zealand Holidays store. If there is upgrades to be done you will receive an email inviting you to make an offer to upgrade to the next cabin class. Passengers whose offers are accepted will receive email confirmation several days prior to travel.
This is awesome!