The British pilots' union, BALPA, has said it has served notice to Ryanair of its intention to ballot members for industrial action over pay and conditions.
It says it will ballot members next week asking them if they're willing to strike.
The strike action, it says, may take place on the week beginning August 19th.
The union say it understands that pilots' unions in Spain, Ireland, Sweden and Germany had made little 'meaningful progress' in talks with the airline.
BALPA said there were a number of areas of concern for pilots on issues such as pensions, maternity benefits, allowances and a "fair, transparent and consistent" pay structure.
"Our Ryanair representatives have been trying to tackle some of the many issues that result from years of non-recognition of unions within Ryanair," BALPA general secretary Brian Strutton said.
"But we have not been able to make any progress with Ryanair at all on any of our areas of concern."