"This is not about being tough. It is about the future of Lufthansa," Carsten Spohr said in Berlin. "We stand no chance to survive" if the company accepts the workers’ requests.
"There is no more leeway for even better offers when escalation is what is wanted, as opposed to a solution," he said.
The dispute has led to almost 1,900 flights being cancelled Wednesday and Thursday, with hundreds more in danger of being dropped on Friday. Lufthansa failed to stop a one-day walkout called by the Vereinigung Cockpit pilot union in the Frankfurt courts on Tuesday night, and the union retaliated by extending the protest by two more days.
Mr Spohr said the company would have to cull more routes if it accepted the union proposal. The union has asked for raises of about 3.7 per cent for each of the years 2012 to 2017, adding up to an increase of about 20 per cent. Lufthansa offered a 2.5 per cent gain.
"We want to be able to grow again, within the group, and also at the core Lufthansa brand. That’s what we aim for. We want to stop shrinking and start going again. In order to be able to do that, we need competitive structures," Mr Spohr said.