Nearly 1,000 flights have been grounded as pilots at German airline Lufthansa start a second day of strikes.

Reports coming out of Germany suggest that some 140,000 passengers have already been affected in a row over Lufthansa cost cutting.

The pilots are striking over retirement benefits, pay as well as Lufthansa's plans to expand low-cost operations.

The pilots also want an end to Lufthansa’s plans to expand Eurowings.

This is the 13th walkout by Lufthansa pilots over the past 18 months.

The striking pilots say there will more strikes unless Lufthansa officials improve their offer to settle the dispute over cost cutting.

"If there's no new offer from Lufthansa we will call for a further strike," Reuters quoted Vereinigung Cockpit spokesman Markus Wahl as saying.

Lufthansa says it must slash costs in order to compete with budget rivals such as Ryanair which have already been targeting the German market.

The German airline had tried to stop the strike with a temporary injunction. However, two German courts ruled in favor of the pilots' union, on Tuesday night.