Hundreds of passenger planes are sitting on the tarmac at airport across Europe, going nowhere, as cabin crews working for Lufthansa went on strike.

Flight attendants walked off the job at midnight Friday, part of an ongoing feud with the German carrier over pay and outsourcing.

Lufthansa canceled about 1,200 flights in advance of the strike and took out newspaper ads Thursday apologizing to customers. The company also criticized the workers, saying the strike was “disproportionate.”

The dispute between Lufthansa and the union representing about 12,000 of the airline's flight attendants caused a number of smaller work stoppages earlier this week.

The strike has affected lights to and from Frankfurt, London, Paris, Moscow, Istanbul and Boston.

A statement on Lufthansa's website says the airline will do its “utmost best to minimize the impact on its customers.”

The carrier is also offering customers traveling within Germany to exchange their plane tickets for train vouchers with Deutsche Bahn.