Roamy here. I was looking through this day in history for post fodder and saw that on February 5, 1918, Stephen Thompson shot down an Albatros D.III fighter. He is credited with being the first person in the U.S. military to shoot down an enemy aircraft. Thompson was flying as a gunner-bombardier in a French Breguet 14.
Thompson’s uniform from this mission is on display at the USAF Museum in Dayton.
As seems to be the case with history, there is a footnote. Thompson was the first U.S. serviceman to shoot down an enemy aircraft, not the first American. That was Kiffin Rockwell, who shot down a German plane on May 18, 1916. Rockwell joined the French Foreign Legion and was later an original member of the Lafayette Escadrille, an American volunteer fighter squadron.
There is some confusion between the Lafayette Escadrille and the later group called the Lafayette Flying Corps. The Escadrille was originally 38 American pilots with five French officers; the Lafayette Flying Corps was over 200 American volunteers. Once the U.S. entered the war, both Lafayette groups were disbanded and the men transferred to the 103rd Aero Squadron.