To arrive in St. Sebastian by plane we strongly recommend you to arrive in the Bilbao Airport. From here, you have a direct bus to St. Sebastian every hour, but we, from Aranzadi, will organize a private transfer service to pick up you at the airport.
Other alternative and nearby airports are the ones at Biarritz, Pamplona or St. Sebastian. This last is placed at the locality of Hondarribia, situated ca. 20 km. far away from St. Sebastian. It is a small, local and rather expensive airport, only offering local flights to Madrid or Barcelona.