Virgin Australia was undertaking a capital structure review, which also almost certainly meant a further capital-raising.
Air New Zealand stated it did not want a large equity position in Virgin as it focused on its own growth opportunities, Ms Kinnaird said.
"While the existing equity stake adds certainty to Air New Zealand's important Tasman alliance with Virgin, it is by no means necessary,'' she said.
Shareholder loans provided by Air New Zealand, Singapore Airlines, Etihad and Virgin last week totalling $A425million ($NZ471million) gave Virgin Australia breathing space ahead of a likely dilutive capital raising.
Air New Zealand's apparent decision to exit rather than increase its investment signalled the realisation any strategic benefits of owning an equity stake in the Australian airline were more than outweighed by the adverse financial reality of providing more capital, she said.
Air New Zealand's net investment in Virgin Australia amounted to $417million.
On a mark-to-market basis, it was now worth about $345million.
Any divestment might need to be undertaken at a discount to the current market price.
While Air New Zealand could walk away absorbing a sizable loss on disposal, it might be the lesser of two evils given the capital demands of Virgin Australia, Ms Kinnaird said.
A disposal at the current Virgin Australia share price would in isolation dilute Forsyth Barr's 2017 reported profit forecast for Air New Zealand by about 5%.
An Air New Zealand exit would leave three strategic holders: Etihad (24.2%) Singapore Airlines (22.8%) and Virgin (10%).
If any of those wished to increase their stake, with the exception of Virgin up to 20%, they would likely have to make a full takeover offer, she said.
The options
Stay: Air NZ would probably need to provide more permanent capital to Virgin Australia with questionable returns.
Go: A Virgin Australia exit would dilute forecast 2017 full-year earnings by at least 5%.
