Severe disruptions to Air France flights are expected after pilots began a four-day strike against legal changes to the retirement age.
Two-fifths of the airline's long haul flights and half of all other services were cancelled as a result.
Disruption to flights operated by partner airlines, including Brit Air and CityJet, will not be as great, chairman Jean-Cyril Spinetta said.
He said the strike would cost the airline 100m euros ($127m; £86.1m).
In an open letter to the carrier's pilots, he called the strike "dangerous", given the financial and economic crisis that has severely affected the airline industry.
With the cost of the strike equal to one of the carrier's 777-300 fleet, he warned that the strike could have a detrimental impact on careers.
Traveller disruption
Mr Spinetta also said the strike was "unnecessary" because the postponement of the retirement age from 60 to 65 was beyond the firm's control, having been passed in parliament.
In addition, pilots will still be able to decide whether they want to retire at the age of 60 while paying the same pension contributions.
The strike is likely to cause chaos for weekend travellers with more long-haul flight cancellations expected.
The airline, which is part of Air France-KLM, said it would update its schedule daily on its website.
A toll-free number has also been set up.
Further havoc for passengers was caused by a fifth day of wildcat strikes by air crew employed at loss-making Italian airline Alitalia in protest against its proposed sale to the Cai investor group, which would probably lead to job losses.
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