American Ninth Army units moved though the area in early September 1944, heading towards Saint-Quentin. The airfield was seized and turned over to the United States Army Air Force (USAAF). IX Engineer Commands 846th Engineer Aviation Battalion moved in around 7 September 1944 and started a quick rehabilitation of the base to allow use by American aircraft Designated Advanced Landing Ground "A-71 Clastres Airfield" it was declared operationally ready for combat units on 9 September, only a few days after having been captured from German forces. Although operationally usable with one runway, Athies was still a wrecked base from the Allied air attacks and what was blown up by the Germans as they withdrew. The Americans worked with what could be repaired and moved in what equipment was necessary to conduct combat operations, the rest was done with tents.

Under American control, Ninth Air Force used the base for several units. Known units assigned to the base were:

387th Bombardment Group (387BG), from 30 October 1944 until 29 April 1945, flying B-26 Marauders

367th Fighter Group (367FG), from 8 September 1944 until 28 October 1945, flying P-38 Lightnings

One of the early missions of Clastres was to provide much needed fuel for the ground troops fighting on the western front. On September 11, 1944, the 467th Bombardment Group (B-24 Liberators) began a period of ferrying operations to carry gasoline to France, called Operation TRUCKIN'. Men from the Group were assigned to France to perform the necessary duties in connection with TRUCKIN' operations. The first airfield used was Orleans/Bricy south of Paris, but this was soon changed to Clastres, and it was to here that most of the Group's planes flew. In addition to the 467th's own aircraft, a number of war weary aircraft from other groups were also used. Skeleton crews were used, and at first the gasoline was carried in five-gallon cans unloaded by the crew at the destination. Later bomb-bay tanks and P-47 belly tanks were installed in the planes and a pumping station was installed at Clastres.

When the combat units moved out, Clastres was turned over to Air Technical Service Command to become an Air Depot and later, during the summer of 1945, a storage depot for large numbers of surplus aircraft, whose units had returned to the United States by ship. Clastres airfield was closed on 30 November 1945 and turned over to the French Air Ministry.