Madridmanjim, in the past 5 years all my trips between Spain and the US have been via London. The only real hassle is a bit of a wait in Heathrow airport, usually about an hour and a half, but for me, the savings and the great service on British Airways' transatlantic flights make it worthwhile. (By the way, British Airways is currently advertising great fares here for summer travel to Europe. You may want to check them out.)