Trade unions in France and Belgium are threatening budget airlines easyJet and Ryanair with strike action over the Christmas period.
The potential walkouts could hit fliers planning to spend Christmas abroad as the row over airport workers' rights and cabin crew pay continues.
The SNPNC-FO union has told easyJet that there is a "very significant risk" of Christmas holiday strikes while trade unions ACV Puls and CNE in Belgium have told Ryanair that "staff will express their anger" during the festive period if demands are not met.
The French union, Syndicat National du Personnel Navigant Commercial, is threatening strike action over an ongoing salary dispute.
The union issued a warning last week which read: "The SNPNC-FO, Syndicat National du Personnel Navigant Commercial, representing the hostesses and stewards of the company EASYJET in France, warns today of a very significant risk of work stoppage for cabin crew during the end-of-year holidays, related to salary negotiations.
"After more than two years of colossal efforts made by hostesses and stewards in France, during which our working conditions have deteriorated sharply due to serious strategic errors for which management alone is responsible, easyJet is offering salary increases this year not even covering inflation, and rejecting the main elements of our demands."
Christian trade unions ACV Puls and CNE are also threatening strike action against Ryanair due to their treatment of airport workers in Belgium.
They sent a letter to the budget airline which explained: "Ryanair decided to close (temporarily according to them) the Brussels base: it had been proposed to the workers of the base to work in Charleroi.
"But for the future, Ryanair changed its mind and decided to have them work in blocks of a few days in other European bases. This is perfectly illegal."
They said that should there be no resolution, they may consider strike action, stating: "The end of year festivities are approaching, and if nothing changes, there is a high probability that staff will express their anger in that period."
No strike dates have been announced as both the French and Belgian unions hope that the airlines will continue negotiations.
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