Corp/Sgt Robert A Williams USMC was training to be a Naval Air Pilot at the time. He qualified and ended up in "VJ Squadron GM Q S Second Brigade Managua Nicaragua" in March 1930 -
which I think is this
http://www.aeroflight.co.uk/waf/usa/...SMC-VMJ152.htm
And then I cannot find him after that.
He enlisted 28 Nov 1927 and was initially a Plane mechanic and served previously in Nicaragua and San Diego