The calculated distance (air line) between Cergy-Pontoise and Aulnay-sous-Bois is approximately 20 miles respectively 32 kilometers.
By car or train, the actual journey to Aulnay-sous-Bois is certainly longer, as only the direct route (as the crow flies) between Cergy-Pontoise and Aulnay-sous-Bois has been calculated here.
Air line (approximately)
32 kilometers
17 nautical miles