About 160 pilots flying for Air Nelson begin a three day stoppage from midnight on Friday until Sunday night in a long running dispute over pay and rosters.
Air Nelson is a subsidiary of Air New Zealand and the national carrier is criticising the Airline Pilots Association members for beginning the stoppage during the school holidays.
Air Nelson says non-union pilots will keep nearly half of its services operating.
The company's general manager for short haul airlines Bruce Parton says the strike will disrupt the travel plans of about 10,000 people.
Mr Parton says he considers the timing of the strike for the school holiday period very cynical, particularly as the parties are due to go to mediation at the end of this month.
Air New Zealand says the pilots work an average of 31 hours a week and their claims would reduce that to about 25.
However, the union says Air Nelson pilots want a clear weekend off every four weeks like other Air New Zealand pilots, and haven't had a pay rise in two years.