Frankfurt airport, Europe's third busiest, was hit with a fresh wave of strikes on Sunday after pay talks with management broke down.
The latest action, which follows earlier strikes, got under way at 8pm (GMT) and was expected to last until 4am on Thursday.
Lufthansa announced the cancellation of 140 flights on Monday, particularly short- and medium-haul journeys.
About 80 percent of long-haul flights would not be impacted, the airline said.
Some 200 apron control staff - who direct aircraft in and out of their parking positions - have been striking since February 16. They want higher pay, increased bonuses and shorter working hours.
Talks with airport operator Fraport broke down Friday, opening the path for a new strike. Fraport insists it had made concessions "on many points in the union's extremely high demands".
Frankfurt airport, Germany's main hub, is Europe's third busiest after London-Heathrow and Paris Charles de Gaulle.