The US military is being stretched thin by the American-led air war against the Islamic State (IS), US Air Force Secretary Heather Wilson said Thursday.

The US-led coalition fighting IS in Iraq and Syria dropped more than 5,000 bombs on the militant group in August, setting a record for the three-year campaign. But the Air Force has just 55 active fighter squadrons, an almost 60% drop from the first Gulf War in 1991, as it faces arbitrary budget cuts and a shortage of planes and pilots.

“The Iraqi people are taking back their own country from this vicious group and ideology with the assistance of United States airpower and intelligence,” Wilson said at the Center for Strategic and International Studies, a Washington think tank. “The problem for us is that the Air Force is still heavily committed, even if we reduce the number of ground forces worldwide.”

While the Air Force’s ability to gather intelligence has improved, allowing it to strike 54,000 IS targets since 2014, the mission is “wearing our people out,” said Wilson. Each coalition fighter jet is refueled four or five times on every mission, requiring as many as 65 tanker missions every day in the Arabian Gulf, she added.