SAS cabin crew based at Heathrow plan four days of Christmas strike action in a pay dispute.
More than 130 flight attendants based at the London hub aim to walk out on December 22, 23, 24 and 26.
The Unite union, which represents the staff, said the Scandinavian carrier has only offered a 3.5% pay increase which, with inflation currently at 4.3%, represents a real-term pay cut.
Flights to Scandinavia will be “severely affected” with far fewer crew available during the busy festive period, the union claimed.
Unite regional officer Callum Rochford said: “SAS Airlines needs to come back to the negotiating table with a proper pay offer for cabin crew or face the wrath of angry passengers for a dispute of its own making."
The union’s general secretary Sharon Graham said: “Scandinavian Airlines publicly praise their cabin crew yet in private it is cynically trying to short change them.
“This is totally unacceptable when the airline depends on their expertise and passengers rely on them for safety.”
Travel Weekly has approached SAS for comment.