German pilots are set to stage the first major strike in the low-cost carrier’s history.
Union Vereinigung Cockpit (VC) made the call following similar threats from unions in Italy and Portugal who urged their members to walk out over pay and working conditions.
The airline’s Dublin based pilots also threaten to take industrial action.
The move comes after disruption in the summer caused by a shortage of pilots, many of whom had moved to rival firms.
Europe’s largest short-haul airline now faces major flight disruptions over the Christmas holidays.
Vereinigung Cockpit says: “Ryanair can stop the German industrial action right now by declaring the willingness to negotiate proper terms and conditions of work and remuneration, a last chance is still being offered”