Lufthansa airlines faces four-day strike in April by pilots, intensifying the industrial unrest gripping Europe’s airline sector.

Vereinigung Cockpit, the German pilots’ trade union, announced it would restart industrial action on April 13 after the failure of talks on future job security, re-igniting one of Germany’s most bitter workplace conflicts.

The announcement came as a blow to Lufthansa’s management as Europe’s largest airline by revenues seeks to rebuild profitability after the worst downturn in commercial aviation history. A shutdown of its services would cost at least €25m a day.

Last month, at short notice, Cockpitcalled on more than 4,000 pilots to stop work for four days. The union argued that Lufthansa pilots’ pay and conditions were being undermined by the company’s increasing reliance on foreign subsidiaries such as Austrian Airlines and British Midland, as well as Lufthansa Italia.

Lufthansa took legal action, claiming Cockpit’s actions were disproportionate. After the stoppage had lasted less than 24 hours, the two sides agreed at a court hearing to return to the negotiating table.