Thousands of UK air travellers face possible delays and cancellations tomorrow due to planned industrial action by French air traffic controllers.
The strike will have the biggest impact in the southern area of France.
But it is expected that the industrial action will also have an effect on all flights that fly over France.
Budget airline easyJet has already warned passengers of possible flight disruption and other UK carriers, including British Airways, are bound to be affected as well.
EasyJet said it had been asked by French civil aviation body the DGAC to reduce its flights from both Paris Charles de Gaulle and Paris Orly airports to southern European destinations by 30 per cent. Flights to Basel, Bordeaux, Lyon, Marseilles and Toulouse are also likely to be impacted.
EasyJet said that more than 70 per cent of its flights operate through French airspace and there was "a risk of late-notice cancellations depending on the severity of the effect of the strike action".
EasyJet went on: "All passengers due to travel on cancelled flights will be advised via email and details of these cancellations will also be listed on our website.
"We therefore strongly recommend that passengers check the status of their flight on http://www.easyjet.com before travelling to the airport. For any passengers whose flight is cancelled we will offer a full refund or they can change their flight booking free of charge on http://www.easyJet.com.
"We would like to reassure passengers that we will do all possible to minimise the delays and will keep passengers informed of any updates. Despite the fact that this disruption is beyond our control, we apologise in advance for the inconvenience that this will cause to our customers."
Ryanair said it had been advised that tomorrow's strike would last from 6am to 8pm and that all airlines flying to and from France had been required to reduce their flight schedules by 30 per cent.
Ryanair said it was cancelling more than 60 flights and warned passengers to expect delays to other services.
Many of the Ryanair cancelled flights are within continental Europe, but axed services include Luton-Nimes and flights from Stansted to the French destinations of Biarritz, Bergerac and Carcassonne.
British Airways has so far axed a Heathrow-Marseille service as well as a Heathrow-Lyon flight.
BA said: "We are monitoring the situation closely as there is potential for disruption on flights to/from France and flights crossing French airspace to Spain and Portugal."