The dispute revolves around an early retirement scheme and Lufthansa's plans to expand its low-cost operations to win back market share lost to the likes of Ryanair and easyJet, which are expanding swiftly in Germany.

Ten strikes staged by VC last year cost the airline close to 200 million euros in operating profit and affected hundreds of thousands of passengers.

In December, the pilots said they were prepared to enter mediation to resolve the dispute, but only if it included all areas of conflict with management.

Lufthansa rejected that demand, however, saying it was willing to expand talks beyond just early retirement benefits, but that low-cost expansion was not up for discussion.

VC said in a statement on Thursday that further industrial action was "possible and likely" as it meets with its members in the coming weeks.

Lufthansa's pilots oppose the way in which the airline is pushing through low-cost expansion by using a small unit that is not subject to the same collective labor agreements as its Lufthansa and Germanwings brands.

VC also wants to maintain a scheme that enables pilots to take early retirement from the age of 55 and still receive a portion of their pay until regular pension payments kick in. Lufthansa wants to increase the retirement age for new starters.

Lufthansa reiterated on Thursday its stance that it needed to make structural changes to help its passenger airlines compete with rivals.

"Necessary structural changes could so far not be achieved in the cockpit," it said in a statement.

(Reporting by Maria Sheahan; Editing by Kirsti Knolle and Victoria Bryan)

Stocks treated in this article : Deutsche Lufthansa AG, Ryanair Holdings plc, easyJet plc