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Presume by ALK you mean Auckland (AKL)? No one knows when NZ will join the alliance wide upgrade scheme. Given yields & how NZ Airpoints works I assume Air NZ will hold off as long as possible. Did you know that Air NZ considers an upgrade from economy to business class on 747 and 777 aircraft as a double upgrade (since premium economy is more than just a slightly nicer seat)?

It can be hard getting paid business class seats on some flights between AKL and USA, let alone upgrades. This is also the most popular flight for attempted awards and NZ Airpoints upgrades (many airpoints elite complimentary upgrades expire unused because they are so hard to redeem).

So, even if/when NZ joins the mileage upgrade program the practical effect is likely to be nil, at least on this route. Other routes, such as between pacific islands and NZ, and certain non-peak trans-tasman flights, would be more likely.