Security staff at eight German airports went on strike on Tuesday in an escalating pay dispute that means up to 220,000 passengers could be affected by delays or cancellations, airport association ADV said.
Security workers at the smaller Hamburg, Hanover and Bremen airports downed tools from midnight while those at main hub Frankfurt joined them two hours later, with a view to striking until 2000 local time (1900 GMT).
Strike action is also expected in Munich, Leipzig, Dresden and Erfurt, meaning hundreds of flights will be canceled.
The latest walkouts follow strikes at five airports last week and were denounced by ADV as excessive.