Frankfurt - Lufthansa passengers faced chaos on Monday after the airline cancelled virtually all of its flights in Germany due to a strike by staff over pay.
"With the start of today's shift, a strike at all large airports has begun," Martina Soennichsen, a spokeswoman for German trade union Verdi said on Monday.
In Frankfurt alone, 2 000 Lufthansa employees started industrial action beginning at 03:00 GMT.
Overall, around 1 700 flights will be cancelled, Lufthansa said.
That leaves just 20 of its regular European short-haul flights running and only a handful of long-haul flights out of Frankfurt, Munich and Duesseldorf. The strikes will cost the airline tens of millions of euros.
Verdi, which represents 33 000 workers, is asking for a 5.2% pay rise and job guarantees.
Lufthansa made a new offer last week to raise salaries by 1.2% from October this year and a further 0.5% a year later, in a deal that would run for 29 months and would not contain job guarantees.
Verdi dismissed the offer as "scandalous".