The German pilots' union VC called a strike at Deutsche Lufthansa for today and tomorrow after talks broke down over retirement benefits, leading to the cancellation of more than 1,000 flights.
The dispute, over proposed changes to an early retirement scheme for pilots that was developed decades ago, has resulted in repeated strikes this year, affecting thousands of passengers at Germany's largest airline.
The union said the Germany-wide strike would last from midday today to midnight tomorrow for short- and medium-haul flights, as well as from 3 a.m. to midnight tomorrow for long-haul flights. (Flights to Malta from Frankfurt and Munich today arrive earlier. The flights are code-shared with other airlines.)
According to a list on the Lufthansa website, more than 1,000 flights have been cancelled, including a few also on Wednesday and Thursday.
Pilots flying for Lufthansa Cargo will also strike. Flights of budget arm Germanwings will not be affected.
Lufthansa said the strike was completely disproportionate and called for an immediate resumption of talks.
It said it made concessions in recent talks, including a 5 percent pay rise, but reiterated that it would not accept a demand that new pilots, as well as those already with the company, should be able to retire at 55.
Eight walkouts by staff this year has wiped 160 million euros (127.78 million pounds) off the carrier's operating profit, adding to pressure from a stuttering global economy and increased competition.
Lufthansa, which last month lowered its profit guidance for 2015 for the second time this year, is expanding low-cost operations to better compete with budget carriers and Gulf rivals and to outflank the pilots' union.
Lufthansa plans to use other pilots from within the group who are not on expensive collective labour agreements to staff tourist routes, where the brand, which usually focuses on business travellers, is trying to reduce costs.
Passenger transport in Germany has also been disrupted by train drivers' strikes this year. Their latest walkout earlier this month thwarted many Germans' plans to travel by rail to celebrations marking the 25th anniversary of the Berlin Wall's fall.
Like the pilots, train drivers have yet to reach a deal with their employers.