A travel agent says the one-day strike of Air New Zealand staff just before Christmas would be almost unprecedented.

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Urgent talks between Air New Zealand and unions are underway in a bid to stop the strike by the airline's engineers on 21 December that would affect nearly 42,000 people.

The airline has said that the average income of the staff prepared to go on strike is $115,000 but the Aviation and Marine Engineers Association said a lot of that salary is based on overtime.

Spokesperson Stan Renwick said engineers work more than 55 hours a week and fatigue is a big concern.

However, the unions are not the only ones concerned.

Brent Thomas from House of Travel has been in the industry for 21 years and said a strike at the busiest time of the year was huge.

"This will be a major impact, not just on Air New Zealand because people have connecting flights internationally on other airlines and we're going to have to work through each one of those on an individual basis," he said.

"It's very, very large and... almost unprecedented in terms of the numbers who may be impacted."

Mr Thomas said worried customers have already been in touch to find out what was going on.

"We've certainly been fielding some calls from those customers but at the moment it's definitely a wait and see - what comes out of today's meeting and hopefully they can get resolution," he said.

"If not, as days go by, customers will become more and more anxious about what is going to happen."

Andy Bank booked flights months ago to fly from Auckland to Wellington with his partner on the day of the planned strike.

They are planning to meet up with family there and then travel to a bach in Nelson.

Mr Bank said he's not looking forward to the alternative of driving down.

"I know during the holiday season it's probably going to be pretty jam-packed especially if the flights are going to be disrupted," he said.

"I can't imagine what those roads are going to look like."

Mr Bank said he has had no communication from Air New Zealand about the strike.

"It's definitely frustrating to... feel like you're out of the loop," he said.

"You [kind of] have to constantly be checking back in on things."

He said this is not the first time he has had to deal with a lack of information from Air New Zealand.

"The flights we had booked, they ended up changing the route and cancelling the flights to a certain city in Japan that we were going to fly into.

"Same deal there, there was no notification whatsoever and actually just had to find out through friends going... with me that the flight was disrupted and still to this day never received an email or anything from them," Mr Bank said.

Fellow Air New Zealand customer Perrine Gilkison booked flights on 21 December for a wedding in Auckland the following day, but she has some sympathy for the engineers.

"I don't think a strike would be called on the busiest travel day of the year unless there were some serious issues that hadn't been dealt with, so for me I'm just going to play it by ear," she said.

"I think probably there'll still be a way to get up by bus or something."

Stan Renwick said Air New Zealand is offering two pay rises of two percent each, but the union wants at least three percent.

The union negotiating team from E Tū said they are committed to bargaining into the night if needed.