ROME -- Post offices and schools were closed, flights were canceled, buses and trains were idled in Italy Friday as millions of workers stayed home to protest government plans to reform the pension system.

The general strike was called by Italy's three largest and most powerful unions, which also organized some 100 demonstrations in piazzas across the country. Big festive crowds gathered in Rome, Bologna and Naples, where rallies were headed by union leaders and center-left politicians.

The workers heeded calls to protest Premier Silvio Berlusconi's resolve to overhaul Italy's generous pension system by raising retirement ages and the number of years of work required.

Hundreds of flights were canceled, most of them by Italy's flagship airline Alitalia, but foreign carriers also scrapped or rescheduled flights because Italian ground personnel were among the strikes. Among the airlines affected were Air France, Lufthansa, British Airways and KLM.

State railways said about half of its train runs were canceled.

Also striking for the day were factory workers, including at Fiat, the automaking group that is Italy's largest private employer.

Countless students didn't bother going to class as nearly half of all public school personnel didn't show up for work.

Hospitals canceled all but emergency treatment, and many banks were shuttered for the morning.

Italy's last general strike was staged in April last year to protest government-proposed changes to Italy's labor law.

The government reform focuses on giving incentives until 2008 to workers who delay their retirement age, which officially stands at 65 for men and 60 for women. In reality, the average retirement age is closer to 59, due to Italy's generous "seniority" pensions, which allow Italians to retire at age 57 after 35 years of work.

After 2008, workers who still want to retire with a seniority pension would face hefty penalties.

Despite opposition from the unions -- and some divisions within his own conservative coalition -- Berlusconi has vowed to go ahead with his plans, and is aiming to push the pension package through parliament before the end of the year.

The unions say the reform isn't necessary and insist Italy's system is perfectly sustainable. They also lament that they weren't consulted by the government on the plan.