Flights in Spain
An internal flight is is by far the quickest way to travel in Spain if you can book far enough in advance. Turn a 12-hour bus or train journey from Seville to Barcelona into a one hour flight.
Note that if you are travelling from Madrid to Seville or Barcelona, it is quicker to take the AVE high-speed train.
The following airlines fly within Spain.
Iberia is Spain's flag carrier and has domestic flights between most of Spain's airports.
easyJet no longer has internal flights in Spain, but it does fly from Lisbon to Spain.
Flights all over Spain.
Ryanair flies everywhere these days. Just be careful not to pay too much with them.