A photograph of my grandfather, Stephen Peter Barbustiak (sp of last name changed during immigration process). DOB 20 August 1895 in Odorin, present day Slovakia. Married September 3, 1917. I know he served in Eastern Europe during World War One.
The "lollipop-like emblem" on the collar is a balloon, but does not necessarily mean he was in the balloon corps. It indicates he was in the Air Service which began as a balloon corps. In 1917 the Air Service operated both airplanes and balloons.
A Field Pilot's Badge over his right breast would be definitive proof that he was a pilot, its lack does not rule it out.
Unfortunately I cannot make out the medals over his left breast pocket.