Upvote:4
I believe @kimchi lover is correct. The single six-pointed star is that of a Gefreiter, an enlisted man who has been promoted once, roughly equivalent to a NATO OR-2 or US Private 1st Class.
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.