A Lufthansa plane flying above the Fraport airport in Frankfurt in this September 28, 2012 file photo. Airport operator Fraport has warned geopolitical events and further strikes at its main customer Lufthansa could weigh on passenger figures at Frankfurt in 2015.

Reuters/Frankfurt

A pilots strike grounded more than half of Lufthansa's lucrative long-haul flights on Thursday, the latest action to pressure management in a protracted row over early retirement benefits and cost cuts.

Lufthansa is trying to cut costs to levels nearer those of its rivals as it is squeezed by budget carriers Ryanair and easyJet on European routes and airlines such as Turkish and Emirates on long-haul flights.

Including Thursday's strike, the second of three planned for this week, pilots have walked out 13 times since April affecting almost 1mn passengers. Other Lufthansa employees are starting to worry the row could damage the business for good.

"We fortunately have very loyal customers, but if this continues in the long run and we aren't able to offer the reliability we need then it could become a problem for our customers," Peter Gerber, the chief executive of Lufthansa Cargo, told Reuters.

Lufthansa Cargo said all its freight-only flights would operate on Thursday, but the strike would affect the freight it carries in the holds of long-haul passenger planes.

Lufthansa cancelled 84 of its planned 153 long-haul flights for Thursday, affecting 18,000 passengers, a spokesman said.

Pilots' union Vereinigung Cockpit (VC) is extending the strike to short- and medium-haul Lufthansa flights on Friday.

Lufthansa said it was cancelling 700 short- and medium-haul flights on Friday, equivalent to about half its scheduled flights, while another 90 were being cancelled because of strike by Italian air traffic controllers.

Pilot strikes cost Lufthansa more than €200mn ($213mn) in lost operating profit last year. Experience so far shows that bookings drop sharply after a strike is announced, stay low for a couple of days and then recover fairly quickly, a Lufthansa spokeswoman said.

However, continuing strikes could force corporate travel managers to push travellers onto other airlines, especially as Lufthansa mainly serves transfer passengers who could just as easily fly via hubs in London, Amsterdam or the Gulf, independent aviation consultant John Strickland said.

"The only winners are Lufthansa's competitors, whether long-haul or short-haul," Strickland said, adding that it was still crucial for Lufthansa management to push through structural changes to keep up with rivals.

The row involves early retirement benefits that VC wants to keep but which Lufthansa wants to change for new starters.

The pilots also want Lufthansa to enter joint mediation on other outstanding issues, such as pay and bringing costs down on flights to tourist destinations. Lufthansa has rejected the demand.