Tens of thousands of air passengers across Europe have had their travel plans thrown into disarray as hundreds of flights in and out of France were grounded on the first day of a two-day stoppage by air traffic controllers.

Ryanair was forced to cancel more than 20 flights in and out of Shannon and Dublin with routes to France, Spain and Portugal affected by the strike.

Flights with Aer Lingus were less affected and it cancelled just one flight to Paris from Dublin and one going in the opposite direction. The same number of flights are set to be hit today and the airline said all other flights to and from France were unaffected.

EasyJet cancelled 118 flights across Europe, including two scheduled to fly between Belfast and Paris.

Low-cost carriers, which run to tight timetables, are generally worse hit than network operators and so it proved for Ryanair which was forced to cancel 250 flights, with many more cancellations expected.

“We sincerely apologise to all customers affected by this unwarranted strike action and we call on the EU and French authorities to take measures to prevent any further disruption,” an airline spokesman said.

The dispute had been caused by the “selfish actions of a tiny number of French air traffic control workers”, the spokesman said.

A dispute over work conditions and plans to raise the retirement age of air traffic controllers to 59 from 57 sparked the dispute.

The French civil aviation authority (DGAC) said up to half of the flights in and out of France would be cancelled today, the second day of the strike action.

The 4,000 flights that use French airspace each day but do not land should not be not affected, according to the DGAC, though Air Berlin advised on its website that services to Spain, Portugal and Morocco could be impacted.

The state-employed air traffic controllers have threatened further stoppages on April 16th-18th and April 29th-May 2nd, coinciding with spring school holidays in France.