Sounds like you are booked in economy. If you are in a high booking class (Y and B from memory) then you can upgrade with miles using *A mileage upgrade program. Otherwise on NZ flights if not NZ airpoints member you have to be lucky to get an op-up. Other airline *G are behind NZ *E and NZ*G (the two *G levels of airpoints), and also behind supported upgrades (miles, status upgrade vouchers). Note NZ has premium economy on 747/777 a/c which is a separate cabin from economy (ie much more than Y+ is on United) so any op-up from economy is likely to premium economy only, not business. That said, op-ups are very rare (and even more so in the current economic climate) so I wouldn't bother thinking about it.