Pilots fear Iberia's investment in CATair, a new low-cost airline, will lead to job cuts and are demanding guarantees that their jobs are safe. Iberia denies it plans job cuts.
The pilots union known as SEPLA said negotiations with the airline had broken down early Monday after Iberia rejected the union's latest proposals.
It was unclear how many of Iberia's 1,900 pilots would take part in the strike, but the airline feared that 1,500 flights and around 200,000 passengers could be affected over the seven days of the planned strike.
Many passengers have been assigned alternate flights, had their money refunded or were allowed to rebook with other carriers, said Iberia spokesman Jaime Perez Guerra.
Transport Ministry rules requiring minimum service levels during strikes, including one flight a day on each route, mean the routes most affected would be those within Spain and to other destinations in Europe.
Routes like that to Chicago in the United States, Peru, Venezuela and Costa Rica would be unaffected because there is only one flight per day, but the Madrid to Barcelona route, for example, which has 44 flights a day, could be hard hit.
Perez Guerra said Iberia was seeking to have the strike declared illegal through Spain's courts, as it was not an internal airline matter but related to pilots complaining about competition from an outside company.
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