Washington (CNN) The cost of U.S. military operations against ISIS now tops $3.2 billion -- a tab of $9.4 million per day, according to Pentagon estimates.

The bulk of those expenses are daily flying operations by the Air Force. Those flights have accounted for 53% of the total costs so far, with munitions and operational support ranking second at 23% each.

The costs averaged $5.6 million per day in August and September of 2014, when the United States was only fighting ISIS in Iraq. But they've ticked up to an average of $9.9 million per day since then, with operations taking place in both Iraq and Syria.