The German cabin crew union UFO threatened to instigate another bout of strikes following what it called "failed" arbitration talks with Lufthansa on Sunday.
"Even though we have agreed to not disclose the contents of these talks, unfortunately we must state that there was no solution … so we failed," said UFO spokesman Nicoley Baublies in the official statement that was issued late on Sunday.
The union said that they were ready to stage new strikes any time from now, but that they would take place on days other than Dec. 24, 25 and 26.
"Industrial action must be expected against any time from now," Baublies said. "The only thing we can disclose to our passengers is that we will leave out the Christmas holidays."
Read more: Germany: Lufthansa arbitration with cabin crew union falls apart
The threat comes just weeks after a two-day strike saw flights grind to a halt across Germany.
Last month, Lufthansa was forced to cancel 1,300 flightsdue to the strikes on behalf of its 21,000 staff members.
The union subsequently agreed to refrain from further strikes amid ongoing negotiations.
lc/mm (Reuters, dpa)
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