The mission of the three pursuit groups had been clearly defined. The First was to clear the front area of balloons and low-flying German aircraft; the Second and Third Pursuit Groups were to provide high cover for the First, and to escort the day bombers. The S.P.A.D. aircraft of the Second and Third also carried two 25-lb (11-kg) bombs each to bomb infantry at will.

The offensive began on 25 September. The weather closed in the next day and stayed bad into November and the Armistice. There were 10 days considered fit for flying in that time, and only three of them were clear enough to permit useful photo missions. On the last three days of October, Army observation squadrons were finally able to photograph all of the long-range artillery objectives for the Army.

The corps observation squadrons told much the same story, but they had additional problems. The signalling system of pre-positioned panels that linked ground and air units depended on some experience on the ground among the troops who would receive the supplies or messages dropped. The soldiers in the Meuse-Argonne offensive were largely new and fresh, and not used to working with observation aircraft.

The Germans had stationed eight of their best fighter squadrons opposite the corps observation squadrons, but they concentrated their attacks on the day bombers and the observation planes were able to work relatively safely. The 16 balloon companies lost 21 balloons, 15 to aircraft and six to enemy shelling.

It was the fighters that saw most of the action, flying their low-level intercepts under clouds, through rain and fog. On their first day of action—26 September—they shot down five German balloons and six airplanes.