The calculated distance (air line) between Aix-en-Provence and Marseille 15 is approximately 12 miles respectively 19 kilometers.
By car or train, the actual journey to Marseille 15 is certainly longer, as only the direct route (as the crow flies) between Aix-en-Provence and Marseille 15 has been calculated here.
Air line (approximately)
19 kilometers
10 nautical miles