BERLIN/DUBLIN (Reuters) - Some of Ryanair's RYA.I Irish-based pilots served notice of a one-day strike on Tuesday and German pilots' union Vereinigung Cockpit said strike action was also possible in Germany in a growing push for better conditions at the Irish budget carrier.

FILE PHOTO: Ryanair commercial passenger jet takes off in Colomiers near Toulouse, France, October 19, 2017. REUTERS/Regis Duvignau/File Photo

Pilots at Europe’s largest airline by passenger numbers have mobilized in the wake of the announcement of 20,000 flight cancellations by the Irish carrier, which it blamed on a lack of standby pilots due to a failure in its rostering following a rule change by Irish regulators.

Pilots are pushing for better conditions at the carrier and the Irish umbrella IMPACT trade union said Irish-based pilots employed directly by Ryanair and who are members of the IALPA pilots union will withdraw their labor on Dec. 20.

The pilots planning to strike were mostly captains, IMPACT said, predicting either flight disruptions or substantial costs to the airline. It warned of further strike days if agreement is not reached on the airline’s bargaining with staff.

Ryanair, which does not recognize trade unions, promised to “face down” the threatened strike which it said involved less than 28 percent of over 300 pilots based in Dublin.

“Ryanair will deal with any such disruptions if, or when they arise, and we apologize sincerely to customers for any upset or worry this threatened action... may cause,” it said in a statement.

In Germany, Vereinigung Cockpit (VC) said it would not rest until Ryanair agreed to a collective labor agreement.

“We want to agree contracts with Ryanair. We see no other way,” VC president Ilja Schulz told reporters in Frankfurt. Ryanair rejects union representation, saying it prefers to negotiate with staff directly.

Ryanair, which has offered its pilots substantial increases in pay that fewer than a third of its 87 bases have accepted, said it had received no notification of strike action by its German pilots.

“If any such action takes place, Ryanair will deal with it head on, but we will not deal with or recognize the Lufthansa pilots union VC, regardless of what action – if any – takes place,” it said in a statement.

The German union joins those in Italy and Portugal, which have also announced plans to strike. Italian pilots are due to stage the company’s first ever strike by pilots on Friday.

VC’s Schulz declined to say when and where the strikes in Germany would take place, but that the union would give notice and that no walkouts would take place from the afternoon of Dec 23 and until the end of Dec 26.

During a long-running dispute with Lufthansa LHAG.DE over pay and conditions, the union typically gave 24 hours' notice of strike action.

Several analysts have expressed scepticism as to whether the Ryanair employment model is under threat.

“We are not saying that this is not a difficult period for Ryanair and that there are not deep divisions between pilots and management that are yet to be bridged, however, what we are saying is that the headlines are worse than the reality on the ground,” Goodbody analysts wrote in a note before the two announcements.