Ryanair is cancelling dozens of flights after pilots and flight attendants in Germany started a one-day strike over pay and conditions, union officials said.
The Cockpit union said the 24-hour strike began at 3am Wednesday and would affect all the airline's bases in Germany, including Frankfurt and Berlin.
The union, representing pilots, is being joined by the ver.di union representing flight attendants based in Germany.
Ryanair is expected to cancel 150 flights to and from Germany through until Thursday morning.
The unions say the budget airline has not given a satisfactory offer on pay and job conditions, but Ryanair says its proposals have been fair and there is no justification for a strike.
Ryanair pilots in several European countries last month staged a strike that prompted 400 flight cancellations.