Around 80,000 passengers are affected by the strike Wednesday that grounded some 750 flights, most of them domestic or within Europe.
The Vereinigung Cockpit union announced that it would extend its strikes to long-distance flights on Thursday.
The union has hit various Lufthansa units with around a dozen short-term walkouts over recent months. The dispute centres on the airline's plans to cut transition payments for pilots wanting to retire early, which the union wants to see maintained.
Traditional national carriers such as Germany's biggest airline are being squeezed both by European budget carriers and major Gulf airlines.