Iberia is planning to launch a low-cost carrier

Union officials said the action had been taken in protest at Iberia's plans to launch a low-cost carrier.

Talks aimed at resolving the dispute ended on Sunday after Iberia failed to convince pilots that their jobs were not in danger, the pilots union said.

Iberia said flights hit by the strike were mainly those serving destinations within Spain.

'Contingency plans'

Flights to the Canary and Balearic islands, Africa, the Middle East and most long-haul flights were operating normally, the airline said.

The company added that it had offered job guarantees to pilots during negotiations with union officials on Sunday.

Five flights were cancelled between London and Spain - three to Madrid and two to Barcelona. The two airlines jointly market some London to Spain flights under a code-sharing agreement.

"We are working on contingency plans to ensure that as many British Airways customers who are booked on Iberia flights can get to their destinations," a BA spokesman said.