Severe disruptions to Air France flights are expected after pilots begin 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 though the strike is thought will cost the airline 100m euros ($127m; £86.1m).

In an open letter to the carrier's pilots, chairman Jean-Cyril Spinetta 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 threatened that the strike could have a detrimental impact on careers.

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 lead to job losses.