German pilots' union VC said late on Friday that talks with carrier Deutsche Lufthansa over early retirement benefits have broken down and new strikes are possible at any time, although not at Christmas.
Lufthansa said the airline had made concessions in recent talks, including a 5 percent pay rise.
But it reiterated in emailed comments that it would not accept a request that new pilots, as well as those already with the company, should be able to retire at 55.
"From now, strike action is to be expected again at any time at Lufthansa, Lufthansa Cargo and Germanwings," the union said in a statement. A spokesman later added that no strikes were planned at Christmas, but declined to give further details.
The row is over proposed changes to an early retirement scheme for pilots that was developed decades ago, when they had to stop work at age 55.
"Unfortunately, Lufthansa's management has not seized upon our proposals for compromise and continues to insist on their maximum demands," the statement said.
The dispute has resulted in repeated strikes this year, affecting thousands of passengers of Germany's largest airline.
Eight walkouts by staff this year wiped 160 million euros ($200 million) off the carrier's operating profit, adding to pressure from a stuttering global economy and increased competition.
Lufthansa last month lowered its profit guidance for 2015 for the second time this year, hitting its shares.
Passenger transport in Germany has also been disrupted by train drivers' strikes this year. The latest walkout earlier this month thwarted many Germans' plans to travel by rail to celebrations marking the 25th anniversary of the Berlin Wall's fall.
Like the pilots, train drivers have yet to reach a deal with their employers.
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