Korean Air assured customers flight disruptions will be minimal over the holiday period as pilots began a planned 10-day strike on Thursday.
It affected some flights and airline management says it expects about 90% to operate as normal.
It is the first pilot strike for more than a decade and the result of a long running wage dispute.
The pilot union had demanded a 29% increase in salary while the airline offered just 1.9%.
Korean Air said 18 flights, including four international services, were cancelled on Thursday out of a total 203 scheduled lights.
Passengers wishing to change flights can do so free of charge or alternatively receive a full refund.
"The company is making all necessary preparations to minimise inconvenience of its passengers, and to make sure there will be no gap in the safe operation of flights," an airline statement said.
