The calculated distance (air line) between Aulnay-sous-Bois and Montfermeil is approximately 5 miles respectively 8 kilometers.
By car or train, the actual journey to Montfermeil is certainly longer, as only the direct route (as the crow flies) between Aulnay-sous-Bois and Montfermeil has been calculated here.
Air line (approximately)
8 kilometers
4 nautical miles