The airline has canceled 800 flights from Germany on Friday and has warned that disruption could continue over the weekend.
Pilots at Germany's airline Lufthansa started a planned 24-hour strike shortly after midnight on Friday.
It forced the carrier to cancel 800 flights, impacting about 130.000 passengers.
Which flights are affected in the strike?
All Lufthansa flights departing from Germany on Friday are included in the strike, affecting schedules in the major hubs of Frankfurt and Munich in particular.
Summer holidays are currently coming to an end in several German states, meaning a number of families face inconvenience.
Passengers were advised to travel by train or rebook their flights for another day instead of coming to the airport as travel chaos was expected.
Swiss, Austrian, Brussels and Eurowings, all Lufthansa subsidiaries, are not expected to be affected by the strike. Their schedule will continue without changes, the company stated.
Flights departing from outside of Germany are expected to operate as scheduled, if aircraft and crews are already abroad.
The airline also announced that "isolated cancellations or delays" over the weekend were a possibility.
What are the pilots demanding?
The pilots' union Vereinigung Cockpit (VC) called for the strike on Thursday night after collective bargaining negotiations with the company failed.
VC says it is demanding a 5.5% pay rise for its more than 5,000 pilots alongside automatic inflation adjustments for 2023.
Spokesperson Matthias Baier said they hadn't received a "sufficient offer" on Thursday, calling it a "sobering and missed opportunity" on side of Lufthansa.
Earlier on Friday, Lufthansa published details of the offer it said the trade union had walked away from. The last offer proposed a blanket increase of €900 ($896) per employee.
The company said this would signify an increase of 15% for pilots early in their career and 5% for experienced captains, based on salaries from the latest 18 months.
The airline is arguing that VC's demands would increase staff costs in the cockpit by 40%, describing the increase as "unreasonable," as it doesn't take into account the impact of the coronavirus pandemic.
"We have no understanding for the VC's call to strike whatsoever. The employer side made a very good and socially balanced offer — despite the continuing burdens of the coronavirus crisis and the uncertain prospects for the global economy," Michael Niggemann, board member for human resources, was quoted as saying.
"This escalation comes at a cost for thousands of customers."
Lufthansa called on the union to return to negotiating table.
Continued summer of travel chaos
Due to staff shortages and strikes, thousands of flights have been canceled this summer. Long queues at major airports frustrated travelers and put airlines under pressure to improve working conditions for their staff.
The pilot's strike comes following a deal reached with ground staff by Lufthansa's management in August. A threatened walkout had forced the compan to cancel more than 1,000 flights.
Lufthansa's subsidiary Eurowings could face a similar situation if it doesn't come to an agreement with their pilots. On Wednesday, captains voted in favor of strikes amid a wage dispute. However, no date is planned yet as negotiations are to continue next week.
