Go through your results for flights to San Sebastian in Spain with Netflights. The most popular airlines for this route are British Airways & Iberia Airlines, with British Airways claiming the top spot. Although Iberia Airlines usually has the best prices, it's best to double check what's available for your travel dates.
Flexible on dates? Conducting your search by month allows you to compare prices to San Sebastian throughout the year. Accommodation prices will also be higher at this time of year.
San Sebastian receives 11 direct and indirect flights every week, but the cheapest airline is normally Iberia Airlines. So, if the flights to San Sebastian don't work for you, you could always try searching for flights to other airports in Spain.
Looking at a few different departure airports will give you even more choice. See what you can find. And remember, it's best to book your flights in advance wherever possible.