A pilot strike will force German airline Deutsche Lufthansa AG to cancel about 1,500 flights, disrupting service for hundreds of thousands of air travelers. The union, which represents about 5,400 pilots, plans to expand the campaign on Tuesday to include long-haul flights, according to reports.

“Lufthansa insists on its maximum demands and has shown absolutely no willingness to compromise,” Vereinigung Cockpit union spokesman Joerg Handwerk told Bloomberg. Monday marks the eighth time this year that the union’s pilots have refused to work.

The Lufthansa pilot strike will affect all flights with Airbus A380, A340, A330 and Boeing 747 aircraft, the Wall Street Journal notes. Pilots won't work from 1 p.m. local time on Monday until 11:59 p.m. on Tuesday night. The latest strike is “not understandable and in no way proportionate,” Lufthansa said in a statement.

The union’s dispute with Lufthansa stems from the airlines’ decision to change its retirement and pension plans, which includes raising the retirement age to 60 from 55. The Vereinigung Cockpit union seeks the restoration of benefits that were slashed in a cost-cutting effort. So far, Lufthansa has offered to reinstitute the benefits for existing employees, but not for new hires.

Lufthansa plans to run about a third of its scheduled flights with volunteer and management pilots. Meanwhile, Germany’s government will reportedly produce a draft law this year that would prevent employees from going on strike if it would result in the disruption of basic infrastructure, the BBC reports.

Germany’s economic ministry acknowledged that the Lufthansa pilots’ strike would “impact some sectors of the economy,” but said it wouldn't change its 1.2 percent growth projection for 2014. Lufthansa stock has dropped 25 percent this year and held at 11.67 euros by Monday, Bloomberg notes.