Airline passengers are suffering huge disruption due to the latest strike by French air traffic controllers (ATCs).
Easyjet, Ryanair and British Airways all cancelled flights on Monday as air controllers began a five-day strike.
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There is a separate call to strike on Tuesday by Air France workers.
Lobby group Airlines for Europe (A4E) warned that more than 1,000 flights are expected to be cancelled this week as carriers have been asked to slash their services by 25%.
Flights serving France as well as those overflying the country are affected, including UK flights to and from Italy, Switzerland and Spain.
Brest and Bordeaux control centres are striking until 7pm on Friday, with the action in the south of France running from 5am on Tuesday until 5am on Friday.
EasyJet cancelled 38 flights on Monday, including four which were due to go from or to the UK.
Ryanair said it was forced to cancel 45 flights on Monday which were due to operate to, from or over France.
British Airways cancelled a number of flights and said it is using larger aircraft where possible to help customers reach their destination.
All three airlines warned passengers to expect delays to flights which are operating.
A4E says 2016 was a record year for ATC strikes, with 41 days affected.
This means more than 35,000 flights have been cancelled due to strikes since 2010.
The lobby group has called for the European Commission and governments to take action to reduce the impact of ATC strikes.
It wants neighbouring countries to be allowed to carry out ATC in airspace affected by industrial disputes.
An easyJet spokeswoman said: "EasyJet is disappointed at this unnecessary strike action causing further disruption for passengers and airlines across Europe.
"As a member of Airlines for Europe, we are working with other airlines to call on governments and the EU to develop an action plan to minimise the impact of ATC strikes on passengers."
She added: "Although this is outside of our control, we would like to apologise to our customers for any inconvenience caused and would like to reassure them we are doing all possible to minimise any disruption as a result of the industrial action."
Ryanair's chief marketing officer Kenny Jacobs said: "We call on the French government and European Commission to take immediate action to prevent thousands of European consumers from having their travel plans disrupted by a tiny group of ATC unions going on strike.
"They cannot stand idly by and allow another summer of disruption and travel misery for European consumers to take place."