Someone correct me if I'm wrong but the OP could still buy future tickets on air nz (but buy them via the virgin website so they're eligible flights) and earn the 4 flights that way. And I think domestic NZ flights are now included (forced by the incoming jetstar competition).

Copy from VA website

Fare type Fare Class Points earn rate per mile
Business Class. C, D, J, Z. 2 Velocity Points
Premium Economy. U, E, O, A. 1.5 Velocity Points
Economy. Y, B. 1 Velocity Point.
Discount Economy. Q, H, M. 0.75 Velocity Points
Discount Economy (Trans-Tasman and Long Haul). V, W, T. 0.5 Velocity Points
Discount Economy (Trans-Tasman and Long Haul). L, G, S, K, P. 0.25 Velocity Points
Discount Economy (domestic New Zealand)*. V, W, T, L, G 0.25 Velocity Points
* Air New Zealand domestic New Zealand fares V, W, T, L and G are only eligible for Points earn for travel from 1 September 2015.

Velocity Points and Status Credits cannot be earned on:

Air New Zealand flights to or from the Pacific Islands and Denpasar, Indonesia. View Pacific Island destinations ineligible for Points earn.
Any domestic New Zealand services booked in a fare class of S, K or P which are operated by Air New Zealand or Air New Zealand link carriers.
Reward Seat Bookings
Fare classes other than as specified above
Codeshare flights (Any flight with an NZ flight number that is operated by an airline other than Air New Zealand Link carriers, including Air Nelson, Eagle Airways and Mount Cook Airlines, and Virgin Australia). not 100% sure but I think this means only the main trunk or A320 flying routes earn and flights to regional centres don't?
Any Air New Zealand flight where AirPoints Dollars have been used as a form of payment irrespective of the fare class flown