BERLIN (Reuters) - Cabin crew at Lufthansa (>> Deutsche Lufthansa AG) staged a second day of walkouts on Saturday, but the German airline was expecting a strike-free day on Sunday.

On the second day of a planned week of protests over failed pension talks, Lufthansa cancelled 520 short-haul flights, affecting 50,000 passengers, virtually all of the flights operated by its main Lufthansa brand out of Frankfurt.

Lufthansa spokesman Andreas Bartels told Reuters TV that long-haul flights were operating as planned.

"The economic damage will certainly go into millions, but we still can't give an estimate and will only know after the strike how much it has cost," Bartels said.

Strikes this year have so far cost Lufthansa 130 million euros.

Queues were building at Frankfurt airport but a spokeswoman said the situation was far from chaotic. It has been booking hotel rooms for stranded passengers and airport operator Fraport (>> Fraport AG Frankfurt Airport Srvs Wrldwd) has also made camp beds available.

The cabin crew union UFO announced on Friday it would not stage any walkouts on Sunday ‎so as to spare the leisure travellers who predominantly travel on Sundays.

The head of the UFO union Nicoley Baublies told Reuters TV that passengers booked on Lufthansa flights between Monday and Friday should expect not to fly.

"We will however make it known during the course of Sunday from which airports and on which concrete routes it will be possible to fly," he said.

Lufthansa is struggling to come to agreement with various staff groups on how to compete with low-cost carriers on short-haul flights and more efficient Gulf carriers on intercontinental routes.

The cabin crew walkout comes after Lufthansa and the union failed to reach an agreement in a long-running row over early retirement benefits and pensions.

The UFO union plans to strike until next Friday, which would make it the longest walkout in the airline's 60-year history.

The carrier is also in talks with its pilots on pay and pensions. They have staged over a dozen strikes in 18 months.

(Reporting by Georg Merziger; Writing by Caroline Copley; Editing by Andrew Bolton)