Hi! I've been able to take my full length golf umbrella on domestic routes, no problem and no questions asked. It was easily able to fit long-ways in the overhead bin (A320s) so you should be fine fitting in 787. And I don't think it counts as one of your carry-on items... well, for me, it didn't anyway. Internationally, I'm sure it'll be fine too - you could always email AirNZ and ask them...?