QF domestic yields are considerable, but bolstered by commanding a majority the internal business traffic, with a huge FF programme that most users don't want to break out of. It has frequency, and a premium product (with a LCC brand to vacuum up the lower yielding traffic) that is beyond what NZ offers domestically at home (and arguably even Trans Tasman in some respects), with its only weakness being a high cost structure. VA has gained a lot of lower yielding traffic, and some corporate contracts, but it has struggled as it is halfway between JQ and QF in terms of product in most respects (A330 business being the exception). QF and VA fought a capacity war for a while that has settled down, there is little benefit in NZ joining that (and needing to tie up capital, staff, scarce airport space in major hubs, lounges). The interest in doing so historically was in a more restrictive environment, whilst both QF and AN ran high cost legacy carriers. I expect NZ to do more flights TT to feed AKL, to venture into Australia domestic would be a sure way to bleed a lot of red ink for many years to come.