Pilots of German airline Lufthansa began a strike on Wednesday, forcing the carrier to cancel most of its flights for the next three days and grounding as many as 425,000 passengers.
The country's biggest airline has said it will cancel around 3,800 flights on Wednesday, Thursday and Friday, as a result of the walkout by pilots who are demanding better pay and retirement conditions.
In addition to Lufthansa's passenger services, the strike, which began at midnight (2200 GMT on Tuesday) and will last until 11:59 pm (2159 GMT) on Friday, will also affect the airline's Germanwings subsidiary and its freight carrier Lufthansa Cargo.
Lufthansa said it has informed passengers via text message or email about the flight changes and offered to re-book them onto other airlines.
Around 60 flights were already cancelled on Tuesday so that passengers changing planes in Germany would not find themselves stranded.
Germanwings said Tuesday it planned to uphold around 600 connections over the three-day period by leasing capacity from other airlines.
The head of the pilots' union Cockpit, Joerg Handwerg, told the local daily Neue Passauer Presse that the walkout was "the only means to force management to compromise" and was a direct consequence of the company's aggressive stance, which is seeking to extend pilots' retirement age beyond 55 at present.
But the industrial action has angered many politicians, even in government, with Transport Minister Alexander Dobrindt complaining in a newspaper interview that "every day of strike is impairing the mobility of hundreds of thousands of people."
And the deputy head of the parliamentary faction of the conservative CDU party, Michael Fuchs, slammed the action as "irresponsible."
There has also been criticism of the pilots from the centre-left Social Democrat party.