Air New Zealand engineers have outlined plans to strike on the airline's busiest travel day of the year, putting Christmas travel plans at risk for tens of thousands of travellers.

The unions (The Aviation and Marine Engineers Association and E tū) representing Air New Zealand's aircraft maintenance engineers, aircraft logistics and related staff served a notice of the planned action only four days before Christmas.

The strike action is set to involve almost 1000 staff members on December 21, and could affect the travel plans of 42,000 customers booked to travel on that day.

The strike action involves a pay dispute, in regard to annual increases in staff pay.

A statement from Air New Zealand said that while the group of engineers has received pay increases annually for the past 12 years, it has so far rejected recent proposals by the airline including an immediate two per cent pay increase followed by a further three per cent increase after 12 months, with a further pay review in mid-2021.

Air New Zealand said the average income of the maintenance engineers, logistics and other staff to strike is $115,000 - and around 170 of them earn more than $150,000.

In addition to the pay concerns, staff are also asking for an extra week of annual leave for employees with five years' service (taking shift workers to six weeks a year), free reserved car parking spaces within 500 metres of their workplace, and the right to renegotiate terms just prior to the busy Christmas season again next year.

Air New Zealand General Manager Aircraft Maintenance Viv de Beus described the proposed strike action as extremely disappointing.

"It would be devastating to see the holiday plans of more than 40,000 hardworking Kiwis and international visitors ruined," de Beus said.

"We have only been in negotiations with this group for six weeks so industrial action is entirely premature. We remain committed to working closely with the engineers' unions to reach a reasonable agreement and avoid strike action if at all possible."