The Austrian Accident Investigation Board assigns the probable cause as:
Continuation of flight with landing gear extended until engine failure due to fuel exhaustion.
- Non compliance of maintaining regulatory fuel reserves; contributing are human factors due to extreme workload and stress, resulting in loss of situational awareness.
- Over reliance on FMS fuel predictions which precluded data of flight with gear down.
- Failure to entertain alternative strategies in low fuel state.
- Ignoring "Fuel Low Level" warning and bypassing Zagreb Airport