PARIS - Strikes across France delayed flights, closed schools, and frustrated commuters Thursday as hundreds of thousands of workers protested government plans to raise the retirement age past 60 - one of the lowest even in Europe.

President Nicolas Sarkozy says retiring so young is now untenable given growing life spans, but unions see his planned reforms to France's overstretched pension system as yet another blow to Europe's cherished social model.

His government wants to raise the retirement age to 61 or 62 - reforms that have been under discussion since well before the current European debt crisis.

Despite Thursday's protests - by nearly 400,000 people, according to the Interior Ministry - France's retirement plans pale before the harsh austerity measures instituted by other European nations, including Greece, Ireland, and Portugal.

Polls show most French voters think something must be done to keep the pension system from collapsing, but ambitious changes have been thwarted by protests in the past.