A German court has rejected a bid by Lufthansa to force a union representing the company's pilots to call off a strike, the latest in a string of walkouts over retirement benefits.

The state labor court in Hesse, which includes Lufthansa's main Frankfurt hub, said Tuesday it rejected the airline's suit and found no grounds to declare the strike illegal. The Vereinigung Cockpit union started a 35-hour walkout at Lufthansa's short-haul fleet mid-Monday and extended it early Tuesday to the company's long-haul services.

The two sides have been fighting for months over the pilots' demand that Lufthansa keep paying a transition payment for those wanting to retire early. The airline, facing tough competition from European budget airlines and major Gulf carriers, wants to cut those payments.