Even though officers of the Flieger-Truppe usually continued to wear the uniforms of their last pre-Air Service unit, they were supposed to attach the shoulder straps of the Flieger-Truppe to this uniform.
These had a light-grey backing and an inner piping in the respective battalion colour (1st Bn - white (illustrated), 2nd Bn - red, 3rd Bn - yellow and 4th Bn - green). On the shoulder strap the officers wore a propeller in yellow metal and their rank pips etc (none for a Leutnant).
This means Allmenröders straps looked like the one in the photo - even though I have no idea as to which Bn he was posted to.
Hth
Karl
Source: Jürgen Kraus, "The German Army in the First World War" (Militaria Verlag)