Aon expects to double its free cashflow from $US1.5 billion ($1.92 billion) in 2012 to more than $US2.3 billion ($2.95 billion) a year by the end of 2017, CEO Greg Case says.

It will invest some of the funds in mergers and acquisitions (M&A), he told the Bank of America Merrill Lynch Insurance Conference in New York earlier this month.

Aon has already stepped up investment in M&A, from $US54 million ($69.26 million) in 2013 to $US479 million ($614.44 million) last year, Mr Case says.

The rise in cashflow will be driven by operational improvement, a decline in uses of cash for pensions and restructuring, and a lower effective tax rate.

Free cashflow grew from $US816 million in 2006 to $US1.38 billion ($1.77 billion) last year, following 425 acquisitions over the past 25 years.

Aon has achieved cost savings through IT and real estate and has received a return on data and analytics, including Aon Broking. It also expects improvements in insurance pricing.