Spain's Iberia is in merger talks with British Airways
Spanish airline Iberia has cancelled 184 flights because of a two-day strike by cabin crews.
A further 184 cancellations are planned for Wednesday as well. The walkout follows similar action in October.
Cabin staff are in dispute with the airline's management over plans for a hiring and wage freeze.
Iberia wants to reduce costs to combat falling profit. The company made a loss of 165.4m euros ($237.2m; £145.7m) in the first half of the year.
Spain's infrastructure ministry is responsible for deciding which routes can be affected. Any destination where there is only one flight a day is not allowed to be cancelled.
That means that most long-haul flights are running as normal - as are routes to the Canary and Balearic Islands.
Unions met on Sunday to discuss Iberia's proposed measures - which include laying off all cabin attendants older than 55 - but no agreement was reached. It wants to save 37 million euros in costs in 2011 and 2012.