Spain's USO and Sitcpla unions say they plan to hold industrial action on Jan. 8, 10 and 13 in a dispute over working conditions.

Ryanair suffered a number of strikes last year by cabin crew and pilots, forcing it to cancel hundreds of flights, after the airline recognised unions for the first time in 2017.

Under an agreement with the Spanish labour authorities, the unions have agreed to operate all flights between Spanish islands and 50 percent of flights between Spanish islands and the Spanish mainland on those days.

But they will only operate 25 percent of flights to and from Spain over 500 kilometres.

"Due to the efforts of the Spanish government minimum services regulator and the support of our pilots and cabin crew in Spain, we expect to operate a full schedule of flights to/from (and within) Spain on Tuesday Jan 8," Ryanair said in a statement.

A spokesman for Sitcpla on Friday said he expected the strike to go ahead as the union saw no sign of compromise from Ryanair.

The spokesman, Mauricio Gabala, said he did not expect that Ryanair would manage to avoid disruption to passengers. "Many passengers will have problems," he said.

(Reporting by Conor Humphries, editing by Louise Heavens)