The calculated distance (air line) between Montagne Blanche and Fond du Sac is approximately 17 miles respectively 28 kilometers.
By car or train, the actual journey to Fond du Sac is certainly longer, as only the direct route (as the crow flies) between Montagne Blanche and Fond du Sac has been calculated here.
Air line (approximately)
28 kilometers
15 nautical miles