The US-led coalition launches about two combat aircraft sorties per hour against Islamic State militants in Syria and Iraq, but how does that compare to previous aerial campaigns?

In this audio visualisation, the BBC's Neal Razzell explores comparisons with the invasion of Iraq, WW2, and Nato's bombing of Serbia in 1999.

Reporting: Neal Razzell; audio mix: James Beard; animation: David Botti. Editor: Richard Knight

First heard: On Background, BBC World Service Radio