Currently two airlines are offering very interesting fares to countries of Central America when departing from Spain. You may either decide to use service of Iberia and fly directly from Europe to Central America (there is one short layover in Madrid on your way). For even slightly cheaper fare you may also decide to use service of American Airlines. These flights are routed via USA and are giving you an opportunity to book a stop-over in Miami. You can decide to book the stop-over on both outbound/inbound flights. The cheapest open-jaw flights either to Panama or Costa Rica are available from just Ł287 (€352) when departing from Barcelona.
To reach the cheapest fare you have to look for flights arriving to Panama City and returning back from Costa Rica (San Jose). You can however book return flights to both countries for just a slightly higher fare.
The flights with Iberia are available to book in travel period between July and December 2014. (same as another Iberia promotion to Buenos Aires, Argentina from Italy). American Airlines allows to book the multi-city flights mainly within November and beginning of December 2014.
As usually we recommend to use Skyscanner to quickly compare your connection possibilities from your homecity. Barcelona is connected with Europe by many low-cost airlines. For instance you may fly with Norwegian and EasyJet from London to Barcelona from just Ł52. (based on current offer in November).
In case of you decide for the routing via Miami with American Airlines do not forget to issue tourist visa or ESTA certificate.
Booking sample of an open-jaw flights from Spain to Central America for just Ł287 below. In this case you would be flying from Barcelona to Panama City on 4th of November 2014 and returning back from Costa Rica (San Jose) to Europe on 18th of November 2014.
Booking sample of a cheap multi-city flights to Central America and USA for just €366 below. In this case you would be departing from Barcelona to Panama on 4th of November. You would be flying then from Costa Rica to Miami on 21st of November. Your final flight from Miami back to Barcelona would take place on 25th of November 2014.