The calculated distance (air line) between Castelnaudary and Aix-en-Provence is approximately 176 miles respectively 283 kilometers.
By car or train, the actual journey to Aix-en-Provence is certainly longer, as only the direct route (as the crow flies) between Castelnaudary and Aix-en-Provence has been calculated here.
Air line (approximately)
283 kilometers
153 nautical miles