Thousands of Irish holiday-makers face serious disruptions next week as French air traffic controllers prepare to join European colleagues in a strike.
"Although the controllers have given an indication that they will strike, they have not said what form the strike will take," said Ms Lilian Cassin of the Irish Aviation Authority.
Ms Cassin told ireland.comthat three possibilities existed. "All French airspace may be closed, grounding all traffic; there may be limited open air space and limited traffic; or flights may be re-routed around the airspace."
The French controllers are due to issue a "notice to airmen" known as a NOTAM early next week in which they will confirm the nature of their action. Only then will passengers know how their flights may be affected.
Air traffic controllers in five European countries are to strike next Wednesday in protest against a European Union plan to harmonise traffic management systems.
The strike could mean disruption for the thousands of air passengers that cross European airspace.
"It is sure to have a big impact on all European air traffic," Mr Alain Serres, national secretary of the National Union of Air Traffic Controllers (SNCTA), said.
The main French air traffic management union will be joined by workers in Portugal, Italy, Greece and Hungary.
The industrial action may be followed by Swiss controllers and some workers at pan-European air traffic body Eurocontrol based in the Dutch city of Maastricht.
The EU’s "single sky" proposal would create a united European airspace for the upper levels of the sky, harmonise varying technical standards between EU states and ensure better co-ordination between military and civil aviation.
A minimum level of air traffic control would be provided, as required under French law, and airlines will know in advance which flights were likely to be delayed or cancelled.
An Air France spokeswoman said: "I have no information on this strike, so for the moment it's too early to say whether it will have an impact on traffic." She added, "All flights are currently maintained. We would advise passengers to contact their carrier the day before they are due to fly."
EU transport ministers will discuss the proposals at a meeting in Luxembourg next Monday but diplomats do not expect them to make a final decision on the plans.