BERLIN: Ground staff of Deutsche Lufthansa went on a strike early on Wednesday, prompting the cancellation of more than 1,000 flights and adding to travel disruptions during the busy summer travel season.

Labour union Verdi had called for the walkout, which is due to run until 6 am (0400 GMT) on Thursday, over its demand for a 9.5% pay hike for around 20,000 workers.

The move had prompted Lufthansa to cancel nearly all flights at its Frankfurt and Munich hubs for Wednesday.

Strikes and staff shortages have already forced airlines including Lufthansa to cancel thousands of flights and caused hours-long queues at major airports, frustrating holidaymakers keen to travel after COVID-19 related lockdowns.

Verdi last month demanded a 9.5% pay rise, or at least 350 euros ($368) more per month for 12 months, for around 20,000 workers who it says are being squeezed by inflation and have been overworked due to staffing shortages at airports.

Lufthansa expects positive quarter despite airport chaos

Lufthansa had offered an increase of 150 euros per month for the rest of this year and another 100 euros more from the start of 2023, plus a 2% increase from mid-2023 dependent on the company’s financial results.

Verdi rejected the offer, saying it was insufficient to offset soaring inflation, which hit 8.2% in Germany in June.

Verdi and Lufthansa have held two rounds of wage negotiations so far.

A third is scheduled for Aug. 3 and 4.