Tens of thousands of Lufthansa passengers faced disruptions Thursday as cabin crew in Germany kicked off a "massive" 48-hour walkout in the biggest escalation yet of a bitter row over pay and conditions.
The strike is affecting all Lufthansa departures from Germany.
A Lufthansa flight between Frankfurt and Malta scheduled for Thursday afternoon was cancelled, but flights between Malta and Munich, operated by Air Malta and code-shared with Lufthansa, operated as usual.
The strike called by Germany's UFO flight attendants' union started at midnight on Wednesday and will last till midnight on Friday.
Lufthansa said it had scrapped 700 flights on Thursday and some 600 for Friday, warning that "around 180,000 passengers will be affected.
The UFO union said the stoppage would impact all Lufthansa departures from German airports.
Last-minute efforts by Germany's largest airline to halt the strike failed after a court in Frankfurt on Wednesday confirmed that the walkout was legal.
Lufthansa said it regretted the inconvenience caused to passengers and stressed that the group's other airlines were not affected.
"We will do everything we can to minimise the impact of this massive strike on our customers," a spokesman told AFP.
The carrier said it would run an alternative flight schedule where possible, and that passengers could rebook their journeys for free or swap their flights for train tickets.
The UFO union argued that the stoppage was necessary because negotiations with Lufthansa bosses were deadlocked.
UFO vice-president Daniel Flohr warned that further strikes could come "at any time".
Lufthansa CEO Carsten Spohr on Thursday, however, held out an olive branch, saying in a statement that he was open to UFO's offer of arbitration talks "in the interest of our customers and employees".
The walkout is UFO's biggest call to action since a week-long strike in 2015 hit Lufthansa with mass cancellations.
It is also seen as a test of strength for the union, weakened by months of infighting that have left Lufthansa questioning its right to speak for cabin crew.
Lufhansa's finance chief Ulrik Svensson declined to put a price tag on the strike, but said these kind of stoppages typically cost "between 10 and 20 million" euros per day.
- Internal disputes -
The union already staged a day-long warning strike last month at four Lufthansa subsidiary airlines, causing several dozen flights to be axed at Eurowings, Germanwings, SunExpress and Lufthansa CityLine.
But the flagship Lufthansa brand was spared the upheaval after management offered a surprise two-percent pay rise to avert the strike.
Since then, however, UFO's Flohr said no progress had been made in talks.
As well as higher pay for cabin crew across the Lufthansa group, UFO is demanding more benefits and easier routes into long-term contracts for temporary workers.
Lufthansa, however, has long argued that UFO no longer has the right to represent its staff following an internal leadership tussle, and has challenged the union's legal status in court.
But Lufthansa's Spohr hinted at a shift in position when he told reporters Thursday he was "confident to overcome the existing legal issues" and was ready to talk with UFO as well as two rival unions.
UFO's internal disputes have cost it support among the Lufthansa group's 21,000 flight attendants, with some members switching to the Cockpit and Verdi unions in recent months.