Almost €10m has been paid out in three years providing security to US troops at Shannon airport.
The cost of providing garda protection between 2006 and 2008 came to €8.6m, while €964,702 was spent on army patrols. This brought the overall amount to €9.56m.
However, the movement of troops is estimated to have been worth around €7m to the airport in 2009.
The cost of providing garda security included €2.8m in overtime payments, more than €1m in expenses and subsistence claims and €4.8m in salaries.
More than 243,000 US troops passed through Shannon airport in 2009.
Justice Minister Dermot Ahern insists the annual bill of more than €3m is justified.