 On June 17, 1913, before flying was shut down again because the airfield was too muddy, Lahm conducted a 21-mile reconnaissance from Ft. McKinley to Alabang, drawing accurate sketches of positions of the 7th and 8th Cavalry on maneuvers there.On July 19, 1913, he passed a Signal Corps-required flying test administered by the Aero Club of America (even though he had received an ACA aviator license in 1911) and received ACA "Expert Aviator's Certificate No.15", which also qualified him to be rated as a Military Aviator.