Air New Zealand engineering staff have voted to strike for three days.

While mediation is ongoing, workers have decided to strike for three days from 21 December.

This period spans three of the busiest days in the airline annual calendar. On 21 December alone, Air New Zealand has close to 42,000 customers booked to travel domestically on its A320 jets and internationally faced potential flight cancellations.

The airline accused just under 1000 engineers of deliberately using Kiwi families' much anticipated Christmas holidays as a bargaining chip.

The airline detailed the average income of maintenance engineers, logistics and other staff to strike — $115,000 – angering unions who accused it of taking an unnecessarily aggressive approach.

E tū's head of aviation, who goes by the name Savage, said on Friday the dispute was not just about pay.

''It's about repeated proposals by the airline weeks out from Christmas to pay them less than colleagues who have already settled, and to cut into key conditions, including overtime rates.''

Those affected included line and hangar engineers, but also store workers and aircraft cleaners, who were covered by the same document and ''who were struggling to get ahead", Savage said.

At this stage, Air New Zealand has not yet announced any cancellations or postponements of flights.

However, a travel booking expert told Newstalk ZB last week that he anticipated massive issues for Air New Zealand should the planned strike go ahead.

Brent Thomas, the commercial director for House of Travel, said the only option would be for Air New Zealand to up-gauge existing flights to add capacity or to add new flights to carry the customers.

"It would cause a significant number of issues, not only for those flying domestically but also those looking to connect with international flights."

Thomas was originally concerned about the impact a single day of striking might have on the days that followed, and a full three-day strike now ups the ante.
Today engineers and Air New Zealand will enter a third day of mediation with the aim of resolving the issues at hand.