The calculated distance (air line) between Longuyon and Saint-Quentin-en-Yvelines is approximately 169 miles respectively 271 kilometers.
By car or train, the actual journey to Saint-Quentin-en-Yvelines is certainly longer, as only the direct route (as the crow flies) between Longuyon and Saint-Quentin-en-Yvelines has been calculated here.
Air line (approximately)
271 kilometers
146 nautical miles