A helpful hint for anyone searching for 787 flights, or for a specific aircraft type (like an A320neo or something else).
You can use the ITA Matrix to search whole months at a time, at the same time entering aircraft types into the search.
Simply head to the search :
https://matrix.itasoftware.com/
Use a oneway search, type in the origin and destination, then select "Advanced controls" and type in "aircraft t:789" (don't add the quotes), finally select "See calendar of lowest fares" (I generally select the first day of the month to search that whole month) select a date and then press search.
The aircraft type in the advanced controls uses the IATA codes so for the Air New Zealand fleet use the following which you can just change out above:
777-200 = 772 (can also using 777 to search both types)
777-300ER = 77W
B787-9 = 789
A320 (the trans Tasman non sharklet fleet) = 320
A320 (the domestic sharklet fleet) = 32A
A320neo = 32N
A321neo = 32Q
ATR72 = ATR
Q300 = DH3
If just searching Air NZ direct flights then put "C:NZ" in the Routing codes box or if searching Air NZ flights with stops use "C:NZ+" (again both without the quotes).