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.