BERLIN (AP) — Ground staff at Lufthansa, Germany’s biggest airline, are staging a several-hour strike that has prompted the company to cancel hundreds of flights.

The ver.di union called workers at several airports including Frankfurt and Munich out on a so-called warning strike ahead of wage negotiations. The walkouts started Thursday at 4 a.m. (0300 GMT; 11 p.m. Wednesday EDT) and are to continue until late morning.