An air traffic controllers strike in France is likely to impact on Irish passengers planning to fly to France, or over French airspace.
Ryanair has cancelled 26 flights to and from France due to the action, which is expected to last for six days.
Aer Lingus says it plans to operate its full schedule, but is warning that customers can expect delays to some flights.
Meanwhile, British airline EasyJet, the second biggest airline in France, is telling customers they will have to cancel about 25% of flights.
The company has advised people against re-booking journeys between today and June 30, because of the likelihood of further disruption.
Cancellations and delays may be significant but are not expected to be as bad as first feared. One of the two French unions involved called off its action after talks.
The unions are opposed to plans for a re-organisation of air navigation in France.