Lufthansa has cancelled 1,350 flights as pilots go on strike in a row over retirement benefits.
The cancellations, of about 48% of scheduled services, will affect more than 150,000 passengers, the airline told the BBC.
The strike, which is the 9th since April, follows a breakdown in talks between the airline and pilots.
Short-haul and medium-haul flights will be affected from 12pm today (11am GMT) until 11pm.
Lufthansa’s long-haul and cargo flights will also be affected on Tuesday.
The airline wants to phase out its early retirement scheme, where pilots are currently able to retire at the age of 55 and receive up to 60% of their pay until the standard retirement age of 65.
Lufthansa said on its website: "The pilots union Vereinigung Cockpit has announced a strike for all Lufthansa short-haul and continental flights departing between 12.00 CEST on December 1st to 23.59 CEST on December 2nd, and for all intercontinental flights departing between 03:00 CEST to 23:59 CEST on December 2nd.
"During the strike period disruptions of Lufthansa flights are expected. Lufthansa is currently working intensely on a special timetable for the strike period. All flights operated by the Lufthansa Group airlines Austrian Airlines, Brussels Airlines, Germanwings, SWISS and Air Dolomiti (operated by OS, SN, 4U, LX, EN) will not be affected."
It said passengers, whose flights have been cancelled, can rebook free of charge to alternative flights and those travelling within Germany whose flights have been cancelled due to the strike may alternatively travel by train with Deutsche Bahn.
