Spanish carrier Iberia is warning that some of its flights might be affected by a general strike in Spain on Wednesday (11 November).
German carrier Lufthansa has also warned of possible disruption.
The 24-hour strike, which starts at midnight on Tuesday, is the first in Spain for 14 years.
The Government has ordered a minimum number of flights to continue, despite the strike.
Between 39% and 64% of international flights are protected, while  between 56% and 80% of flights between the mainland and the Canaries, the Balearics, Ceuta and Melilla will continue to operate.
At Palma, 75% of flights are protected.
Iberia is offering to refund tickets for customers booked to travel on Wednesday on Iberia, Iberia Express and Air Nostrum, or they can postpone their journey up to 26 November 2026.
The Government has ordered the rail services to operate at 75% of community train capacity during peak times on Wednesday and at least one train an hour each way at all other times. Long-distance and high-speed trains will run at 73% and regional medium distance services at 65%.
Train drivers were also on strike on Tuesday and further walkouts are planned on Thursday.
