Ground staff including baggage handlers are protesting against contracts signed with new providers at Spanish airports.

Spain's two main unions UGT and CCOO plan a walkout from Jan. 5 until Jan. 8, disrupting travel over the country's traditional Epiphany holiday.

A member of Iberia's press office said Madrid airport would not be affected, but airports in Barcelona, Palma de Mallorca, Ibiza, Malaga, Bilbao, Gran Canaria, Tenerife and Alicante would.

Spain's flagship airline Iberia, Iberia Express and Air Nostrum had cancelled 400 flights and other IAG partner airlines an additional 300, she added.

Other airlines outside the IAG group that use Iberia Airport Services could be affected, she added, though minimum service legislation meant disruption should be limited.

Paloma Gallardo, the Iberia representative for union CCOO, said the union expected the strike to be observed at all airports, including Madrid. "We hope it will be as much as possible," she said. "The conflict is very serious."

With the strike trailed for weeks amid discussions between the company and unions, "more than 90% of customers have already obtained a solution to the cancellation of their flight," the company added in an earlier statement.

UGT did not immediately return requests for comment.

Spanish commercial airports are operated by state-controlled Aena, which in September hired new contractors for services that were previously provided by Iberia in many airports, angering unions even though the new suppliers committed to retain workers and their working conditions.

Iberia is challenging the new contracts in the Spanish courts and called strike action in the meantime "irresponsible".

The Iberia press office member said only 3,800 of its 8,000 ground service workers were in airports where services were now being run by new contractors and it remained unclear how widely the strike would be observed.

(Reporting by Aislinn Laing and David Latona; Editing by Susan Fenton)