Flights to and from airports in Ireland have been disrupted by an air traffic controller strike that began in France and has now spread to other countries.
Ryanair says 28 of its flights have been affected by the air traffic controllers strike, with CityJet cancelling six flights and Aer Lingus four flights.
French workers are concerned that EU plans to create a single European airspace will see a dis-improvement in their working conditions.
Intending passengers are advised to check the status of their flights with their airline before travelling to airports.
France's main controllers' union said the EU plans are "a direct attack on the public service nature of this sector" and a step towards privatisation.
The IMPACT trade union, which represents air traffic controllers in Ireland, has said its members support their French colleagues' action.
A spokesperson for the union said that staff based at Irish airports share French concerns about EU plans to create a single European airspace.
However, he said that due to legal restraints, workers in Ireland cannot go on strike in protest against EU policy/rulings.
He said they can only take industrial action against their employers.
Transport spokesperson at the European Commission Helen Kearns said the right to strike was well established in the EU, but the right had to be balanced with a certain level of responsibility.
She said the stoppage was having a huge impact on people and business.
Ms Kearns was commenting on a call by Ryanair that air traffic control stoppages in the EU should be made illegal.
She said the single European airspace project had started in the late 1990s.
However, key deadlines had been missed and the EU area was not in a position to deal with a potential 50% increase in flights over the next ten to 20 years.
Speaking on RTÉ’s News at One, Ms Kearns said: "Sadly at the moment passengers across Europe face longer delays and disruption every day because of weak air traffic control systems in Europe.
"The reforms are necessary. They've hit a chord in France and there'll just be a lot of negotiation work to be done there, but they are absolutely necessary."