Strikes at airports in Düsseldorf, Cologne, Dortmund, Hannover, Frankfurt and Munich are taking place, impacting thousands of passengers. German airline Lufthansa has scrapped hundreds of flights.
Ground crews are participating in the mass strikes, which were called by German labor union Verdi in response to a dispute over wage increases. German airline Lufthansa, which is not part of the negotiations, said it canceled around 900 flights in response to the announcement.
Intercontinental flights were the most affected, but even some domestic and European flights were canceled, Lufthansa said.
Air Berlin, Germany's second-largest airline, said it had canceled all domestic flights in Germany until midday local time (1000 UTC) as well as all flights to Munich.
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A new round of negotiations between Verdi and the government will take place on April 28 and 29.
Verdi - one of Germany's biggest labor unions - is demanding a 6-percent wage increase for some 2 million public service employees it represents. It's also calling for a pay increase of 100 euros (USD 112.81) per month for trainees.