Omicron and flu outbreaks among staff have led Finnair to reduce February flights by 20%.
The carrier said there had been “a significant increase in sick leave” at the airline and its partners.
Most cancellations are on routes where Finnair operates multiple daily flights, with customers offered an alternative flight to the same destination on the same day.
Changes will also be made to long-haul flights. The inaugural Dallas service will move from February to 27 March, while the start of a Nagoya service and added frequencies to Osaka are postponed to the summer season.
Customers with cancelled flights also have the option to apply for a refund for unused tickets.