This man, Fred Kustes was a staff sergeant in the US army air corps. What does S.R. of the NS mean on his obituary? [https://www.newspapers.com/clip/37055270/obituary\_for\_fred\_m\_kustes/]

Also, what would someone in the role staff sergeant in the US army air corps do? My understanding is that he was an air traffic controller but I'm not sure if that's really what it was based on the title.

Thank you!