The calculated distance (air line) between Saint-Jean-de-Luz and Ondarroa is approximately 38 miles respectively 61 kilometers.
By car or train, the actual journey to Ondarroa is certainly longer, as only the direct route (as the crow flies) between Saint-Jean-de-Luz and Ondarroa has been calculated here.
Air line (approximately)
61 kilometers
33 nautical miles