As one of the largest airlines in the world, Delta has quite a few long-haul flights. The most common ones, at least that I see frequently, are the flights to and from Amsterdam, Paris, London, Johannesburg, and many more. I love seeing their B767-300ERs come into KBOS from LHR and CDG and EHAM. Such a great sight! Their a330-300's operate many long-haul flights as well, such as the JFK-FCO route, and of course many others.