Spanish carrier Iberia has been forced to cancel 91 flights on 18 December due to planned strike action by its pilots' union SEPLA.
Pilots will strike on 18 December and again on 29 December. Iberia will announce the impact on its 29 December flights at a later date.
SEPLA is taking the industrial action to protest against the creation of low-cost subsidiary Iberia Express, which is scheduled to begin operations at the end of March 2012 with an initial fleet of four Airbus A320s.
The 91 flights affected by the strike on 18 December represent 32% of Iberia's total schedule for that day and are services that are not covered by the Spanish government's minimum services regulations.
Flights operated on behalf of Iberia by Air Nostrum and Vueling will not be affected, nor will services to and from the Balearic Islands, said Iberia.
Flights to and from Africa will remain unaffected, while 17% of long-haul flights will be cancelled. These cancellations will impact flights to New York, Miami, Buenos Aires, Mexico City and Sao Paulo.
"Iberia again appeals to the sense of responsibility of the SEPLA union to call off this strike that has no justification, and that is causing grievous harm to customers and to the airline itself," said the carrier.
"As has been stated on numerous occasions, the creation of Iberia Express will have no negative consequences on the pay or working conditions of any current Iberia employees. On the contrary, Iberia Express will allow the company to grow, become more profitable, and even to create 500 new jobs in the first year."