Public sector workers in France are staging a series of strikes, affecting transport and disrupting schools across the country.
Trade unions have called the strikes over government plans to reform the pensions system and raise the retirement age from 60 to 62.
Hundreds of thousands of people are expected to protest on the streets.
The government fears it will face a funding shortfall and a pension system collapse if it takes no action.
Strike organisers say they have 200 rallies planned and are hoping for at least one million protesters, although they have said that figure might be higher.
Francois Chereque, head of the moderate CFDT union, told French radio he was counting on a "very big demonstration" against "Europe's most violent [pension reform]".
About one in two mainline trains were running in and out of Paris, with three in four Paris metro trains operating, transport officials said.
Some 15% of flights would have to be cancelled between 0700 and 1400 local time (0500 GMT and 1200 GMT) from Paris's main international hub Charles de Gaulle and its other main airport, Orly, the airport authority said.
The education ministry said 32% of primary school teachers stayed away from work and 10% at secondary schools. The teachers' union SNUipp-FSU said more than one in two would strike and several schools were forced to close.
Publicly owned radio stations France Inter and France Info played music to fill gaps in programming.
Print workers joined in, and Friday editions of daily newspapers such as Le Monde and Liberation will not be published.
Strikes were also called in the postal service, gas and electricity providers and numerous private companies.
Strikes by energy workers led to a 7,000 megawatt (MW) cut in power capacity by 1200 local time (1000 GMT) on Thursday, including 6,000 MW in nuclear energy capacity, Reuters news agency reported.
The strikes also had knock-on effects outside France. Freelance journalist Marian Hens told the BBC her flight from Madrid to Barcelona had been delayed by at least two hours because of disruptions to flights from or over France.
Hundreds of passengers were delayed at Rome's main train station on Wednesday when the overnight train to Paris was cancelled because of the strike, reports said. Authorities were putting passengers on buses instead.
And Swiss national railway company SBB said about 60% of trains between France and Switzerland have been cancelled because of the strike.
The reforms to be presented to the cabinet next month will raise the retirement age from 60 to 62 by 2018.
That would affect five million civil servants, many of whom retire at the age of 55, and would target the bonuses and the tax breaks that provide pensioners with - on average - a higher standard of living than ordinary workers.
According to the national pensions advisory council, if the system is not changed, France will face a funding shortfall of between 72bn and 115bn euros by 2050, and that is with optimistic assessments of the recovery.
In another move to rein in public spending, French President Nicolas Sarkozy would not hold the traditional Bastille Day garden party at the presidential palace on 14 July this year, reports say.
The 2009 celebration was said to have cost more than 700,000 euros (£575,000), according to an opposition Socialist lawmaker.
The BBC's Christian Fraser, in Paris, says that as other governments around Europe wield the knife, President Sarkozy knows his country will need to show it is serious about addressing its spendthrift habits.
And in the government's words, it is reform of society that is needed, our correspondent adds.
Under current rules, both men and women in France can retire at 60, providing they have paid social security contributions for 40.5 years. Public sector workers retire on 75% of their final salary.
The proposals must still be agreed by the French parliament in a vote in September - when bigger protests are planned.