The Service and Food Workers Union says 150 Air New Zealand employees are shocked they have been issued with lockout notices.

The airline and the union have been negotiating a collective employment agreement since May.

But Air New Zealand says the negotiations have become untenable and has issued lockout notices, some for up to eight days.

The union's northern region secretary, Jill Ovens, says the workers had just agreed to go into mediation.

Ms Ovens says the workers were not threatening strike action, but were not willing to settle for contracts the other unions had accepted.

Auckland International Aiport says it is untroubled by news of the lockout, adding that there are plenty of other workers within the airport to keep it running.

Council of Trade Unions president Helen Kelly says the airline is behaving aggressively towards workers after having been found last week to have breached nearly 300 good-faith provisions under the Employment Relations Act.

Ms Kelly also says the New Zealand Government should be questioning whether Air New Zealand is acting in the best interests of travellers by issuing lockout notices during a peak season, thereby affecting both domestic and overseas travellers.

She says Air New Zealand customers should write letters of concern to the airline or travel with another company.