On the 15th, the full Allied offensive in the sector began, with operations ongoing from dawn until nightfall. The 27th encountered German formations as large as 30 aircraft. On the 16th the Germans crossed the Marne River at Dormans, however the American infantry outflanked the Germans and were able to hold the line. During the offensive, the 27th continued escort flights of photo-reconnaissance planes so headquarters would be able to know the locations and strength of the enemy forces. By the 29th the Nieuport 28s began to be replaced with Spad XIIIs.