Lufthansa will cancel 3,800 flights this week if a three-day pilots' strike goes ahead as planned.
The German carrier said 425,000 passengers will be affected by the industrial action, which is scheduled to take place on Wednesday, Thursday and Friday.
The strike, protesting pay and contract negotiations, has been called by the Vereinigung Cockpit union.
More than 99 per cent of pilots have voted in favor of strike action to resolve the transition contract issue in a ballot.
Last Thursday, separate strike action by ground staff, baggage handlers and maintenance workers forced Lufthansa to cancel 600 flights (see news, March 27).
The airline said in a statement: "The announcement alone has already caused significant damages since passengers have already rebooked flights and logistic customers have made arrangements with other cargo airlines to secure the transport of their goods.
"During the three-day walkout by cockpit teams, there will only be around 500 short- and long-haul flights by Lufthansa and Germanwings."