29 years later...
I've been collecting the bios of New Jersey residents who served as aircrew with any of the Allied Air Services during the war for the last 29 years, but have yet to come across Milnor's name.
Was his name John K. Milner ? Notice the spelling difference. If so, he was an observer with the 96th Aero Squadron. Not a pilot which would explain why I missed him. The SIgnal Corps, as far as I have been able to determine, did not keep a comprehensive listing of observers that would have saved me a few years of digging !
If "Milner" is your man (or his name is mispelled in the Squadron history), he arrived on 11 September 1918 and was hospitalized at an unspecified date.
I have a brief bio of John Kennedy Milner if he's your guy. I see he was born in Alabama though so may be another man altogether.
I will see what I can dig up on J.K. Milnor in the meanwhile. I will add him to the list of 740 to join the other 8 fliers from Ridgewood....