Kazuo Inamori, a business guru and ordained Buddhist monk who reversed the fortunes of debt-ridden Japan Airlines, has died aged 90, a company he founded said Tuesday.

The entrepreneur was one of Japan's most respected executives, having established electric components maker Kyocera and another firm that later became part of telecoms group KDDI.

He died "of old age" at his Kyoto home on August 24 and a family funeral has since been held, Kyocera said in a statement.

Japan's government convinced Inamori to come out of retirement in 2010 to head Japan Airlines (JAL) after the ailing carrier filed for bankruptcy.

The businessman -- who was 78 at the time -- said he was a "complete amateur" in the transport industry, but promised to "do my best".

His overhaul was successful and JAL shares were relisted on the stock exchange in 2012, less than three years after the airline was forced to delist.

Inamori was an advocate of reducing government interference in business and he was known for his "amoeba management" theory, which grants autonomy to each unit of a company while group members pool their knowledge.

He was also a philanthropist whose close work with Alfred University in the US state of New York led it to rename its engineering department after him.

After stepping down from an active role at Kyocera, he earned the status of Buddhist monk in 1997 at a Kyoto temple, but he did not live a reclusive religious lifestyle.

Kyocera said it planned to hold a separate memorial for Inamori but details had not yet been decided.