Jacinda Ardern has rejected Opposition leader Simon Bridges' suggestion that the Government's stance on unions has "emboldened" them to carry out strikes.

The National leader brought up the issue in Parliament's question time today as Air New Zealand engineer strikes loom just over a week away - putting tens of thousands of travel plans in jeopardy.

"Isn't the reason for the strike that her Government's pro-union stance and union law have emboldened unions in every single field including aviation?" Mr Bridges asked.

Ms Ardern replied with a simple "no" before resuming her seat.

"Are there too many strikes in New Zealand today?" Mr Bridges followed up.

This drew a longer response, in which the Prime Minister pointed to recent successful negotiations with nurses after strike action.

"I acknowledge that the strike action we experienced with the nurses was a negotiation that [the previous] Government failed to resolve and this one did," she said.

Earlier, Ms Ardern said she has appealed to Air New Zealand and its engineers to reach a resolution, saying "no one wants to see that strike occurring" over the Christmas period.

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It comes after aviation unions revealed yesterday the strike notice they had issued last week was for three days - December 21, 22 and 23.

It has been estimated it could impact up to 100,000 travellers.