The calculated distance (air line) between Oberndorf bei Salzburg and Dornbirn is approximately 153 miles respectively 246 kilometers.
By car or train, the actual journey to Dornbirn is certainly longer, as only the direct route (as the crow flies) between Oberndorf bei Salzburg and Dornbirn has been calculated here.
Air line (approximately)
246 kilometers
133 nautical miles