In preparation for Operation Bodenplatte, III. Gruppe was moved to an airfield at Großostheim, near Aschaffenburg on 17 December 1944. Fassong had learned of the planned operation on 5 December at a meeting held at the headquarters of the II. Jagdkorps (2nd Fighter Corps) commanded by Generalmajor Dietrich Peltz, on 5 December. Fassong informed his Staffelkapitäne of the upcoming operation on 15 December without going into the specifics of the target and date. At 06:30 on 1 January, Fassong briefed his pilots of the operation and that their target would be the Asch Airfield (Designated: Y-29) located north-west of Maastricht. At 08:18, Fassong led a flight of 31 Fw 190 A-8 fighter aircraft to Frankfurt where they were joined by other Luftwaffe fighters.
