Given the large number of low-cost airlines that fly to Bilbao Airport (BIO), it’s easy to get cheap flights to Spain from most European cities. Here is a list:
Aer Lingus has flights to Bilbao from Dublin
Air Berlin has flights to Bilbao from Palma de Mallorca
Air Europa has flights to Bilbao from Fuerteventura, Gran Canaria, Lanzarote, Tenerife (North)
Swiftair has flights to Bilbao from Madrid
easyJet has flights to Bilbao from Geneva, Lisbon, London (Stansted), Manchester
Germanwings has flights to Bilbao from Stuttgart
Norwegian Air Shuttle has flights to Bilbao from Oslo (Gardermoen)
Orbest Orizonia Airlines has flights to Bilbao from Fuerteventura, Gran Canaria, Ibiza, Lanzarote, La Palma, Menorca, Palma de Mallorca, Tenerife (North and South)
Ryanair has flights to Bilbao from Barcelona, Gran Canaria, Madrid, Seville, Weeze
SmartWings has flights to Bilbao from Prague
TACV has flights to Bilbao from Sal
Volotea has flights to Bilbao from Venice (Marco Polo)
Vueling has flights to Bilbao from Amsterdam, Athens, Barcelona, Berlin, Fuerteventura, Gran Canaria, Ibiza, Lanzarote, Menorca, Milan (Malpensa), London (Heathrow), Malaga, Palma de Mallorca, Paris (Orly), Santorini, Seville, Tenerife (North), Venice (Marco Polo)
In addition to these, major international airlines like Lufthansa fly to Bilbao.