The Indian head you are describing is most likely the Lafayette Escadrille insignia. This was a very famous French squadron that was made up of Americans flying in French servive prior to US involvment. It was designated N-124 when flying Nieuports, S-124 when flying Spads, and it became Squadron 124 when transferred to the USAS after US entry into the war. If I remember correctly, the Escadrille started combat ops in April-May 1916. The Indian head emblem was adopted sometime in the fall, around October, of the same year. There was another USAS squadron that used a different Indian head emblem but I do not remember which squadron, right off hand. -- Al